diff --git a/lib/mindbody-api.rb b/lib/mindbody-api.rb
index ef100cb..7d77635 100644
--- a/lib/mindbody-api.rb
+++ b/lib/mindbody-api.rb
@@ -18,13 +18,16 @@ def configuration
   end
 
   class Config
-    attr_accessor :log_level, :open_timeout, :read_timeout, :source_name, :source_key, :site_ids
+    attr_accessor :log_level, :open_timeout, :read_timeout, :source_name, :source_key, :site_ids, :username, :password, :prod_mode
 
     def initialize
       @log_level = :debug
       @source_name = ENV['MINDBODY_SOURCE_NAME'] || ''
       @source_key = ENV['MINDBODY_SOURCE_KEY'] || ''
       @site_ids = (ENV['MINDBODY_SITE_IDS'] || '').scan(/-?\d+/).map(&:to_i)
+      @username = ENV['MINDBODY_USERNAME'] || nil
+      @password = ENV['MINDBODY_PASSWORD'] || nil
+      @prod_mode = ENV['MINDBODY_PROD_MODE'] || false
     end
 
     # Make sure site_ids is always an Array
diff --git a/lib/mindbody-api/client.rb b/lib/mindbody-api/client.rb
index 6d17444..9553807 100644
--- a/lib/mindbody-api/client.rb
+++ b/lib/mindbody-api/client.rb
@@ -10,9 +10,13 @@ def call(operation_name, locals = {}, &block)
         @globals.open_timeout(MindBody.configuration.open_timeout)
         @globals.read_timeout(MindBody.configuration.read_timeout)
         @globals.log_level(MindBody.configuration.log_level)
+
+        auth = locals[:auth]
+        locals.delete(:auth)
+
         locals = locals.has_key?(:message) ? locals[:message] : locals
         locals = fixup_locals(locals)
-        params = {:message => {'Request' => auth_params.merge(locals)}}
+        params = {:message => {'Request' => auth_params(auth).merge(locals)}}
 
         # Run the request
         response = super(operation_name, params, &block)
@@ -20,10 +24,41 @@ def call(operation_name, locals = {}, &block)
       end
 
       private
-      def auth_params
-        {'SourceCredentials'=>{'SourceName'=>MindBody.configuration.source_name,
-                               'Password'=>MindBody.configuration.source_key,
-                               'SiteIDs'=>{'int'=>MindBody.configuration.site_ids}}}
+      def auth_params(auth = nil)
+        auth ||= 
+          {
+            :source_name => MindBody.configuration.source_name,
+            :source_key => MindBody.configuration.source_key,
+            :username => MindBody.configuration.username,
+            :password => MindBody.configuration.password,
+
+            :site_ids => MindBody.configuration.site_ids
+          }
+
+        params = 
+          {
+            'SourceCredentials' => {
+             'SourceName' => auth[:source_name],
+             'Password' => auth[:source_key],
+             'SiteIDs' => {
+               'int' => auth[:site_ids]
+              }
+            }
+          }
+
+        if (auth[:username] && auth[:password])
+          params['UserCredentials'] = 
+            {
+              'Username' => auth[:username],
+              'Password' => auth[:password],
+              'SiteIDs' => {
+               'int' => auth[:site_ids]
+              }
+            }
+        end
+
+        params.merge!({"Test" => true}) unless MindBody.configuration.prod_mode
+        params
       end
 
       def fixup_locals(locals)
diff --git a/lib/mindbody-api/ext/savon_ext.rb b/lib/mindbody-api/ext/savon_ext.rb
index d9ed2f4..41606ca 100644
--- a/lib/mindbody-api/ext/savon_ext.rb
+++ b/lib/mindbody-api/ext/savon_ext.rb
@@ -15,9 +15,23 @@ def #{operation.to_s.snakecase}(#{params.join(',')})
                       .join(',')}
             }
             locals ||= {}
+
             client.call #{operation.inspect}, :message => locals.merge(req_hash)
           end
         RUBY_EVAL
+
+        class_operation_module.module_eval <<-RUBY_EVAL, __FILE__, __LINE__+1
+          def #{operation.to_s.snakecase}_with_auth(auth#{!params.empty? ? ',' : ''} #{params.join(',')})
+            req_hash = {
+              #{params.select{|p| p != 'locals = {}'}
+                      .map{|p| "'#{params_key(p)}' => #{p}"}
+                      .join(',')}
+            }
+            locals ||= {}
+
+            client.call #{operation.inspect}, :auth => auth, :message => locals.merge(req_hash)
+          end
+        RUBY_EVAL
       end
 
       # Defines an instance-level SOAP operation.
@@ -31,6 +45,12 @@ def #{operation.to_s.snakecase}(#{params.join(',')})
             self.class.#{operation.to_s.snakecase} #{params.join(',').chomp(' = {}')}
           end
         RUBY_EVAL
+
+        instance_operation_module.module_eval <<-RUBY_EVAL, __FILE__, __LINE__+1
+          def #{operation.to_s.snakecase}_with_auth(auth#{!params.empty? ? ',' : ''} #{params.join(',')})
+            self.class.#{operation.to_s.snakecase}_with_auth(auth, #{params.join(',').chomp(' = {}')})
+          end
+        RUBY_EVAL
       end
 
       # Builds the array of params the
diff --git a/lib/mindbody-api/models.rb b/lib/mindbody-api/models.rb
index e8c4a3e..12685a6 100644
--- a/lib/mindbody-api/models.rb
+++ b/lib/mindbody-api/models.rb
@@ -8,6 +8,7 @@ class Base
   end
 end
 
+require 'mindbody-api/models/resource'
 require 'mindbody-api/models/location'
 require 'mindbody-api/models/client'
 require 'mindbody-api/models/schedule_type'
@@ -29,6 +30,6 @@ class Base
 require 'mindbody-api/models/sale'
 require 'mindbody-api/models/sale_item'
 require 'mindbody-api/models/service'
-require 'mindbody-api/models/resource'
 require 'mindbody-api/models/appointment_status'
 require 'mindbody-api/models/appointment'
+require 'mindbody-api/models/waitlist_entry'
\ No newline at end of file
diff --git a/lib/mindbody-api/models/class.rb b/lib/mindbody-api/models/class.rb
index 4c54e87..3258587 100644
--- a/lib/mindbody-api/models/class.rb
+++ b/lib/mindbody-api/models/class.rb
@@ -22,6 +22,7 @@ class Class < Base
       attribute :end_date_time, DateTime
       attribute :class_description, ClassDescription
       attribute :staff, Staff
+      attribute :resource, Resource
 
       def name
         class_description.name
diff --git a/lib/mindbody-api/models/client.rb b/lib/mindbody-api/models/client.rb
index 96f6bf7..302e69b 100644
--- a/lib/mindbody-api/models/client.rb
+++ b/lib/mindbody-api/models/client.rb
@@ -5,6 +5,7 @@ class Client < Base
       attribute :first_name, String
       attribute :last_name, String
       attribute :gender, String
+      attribute :account_balance, Float
       attribute :email, String
       attribute :email_opt_in, Boolean
       attribute :address_line1, String
@@ -23,6 +24,10 @@ class Client < Base
       attribute :photo_url, String
       attribute :username, String
       attribute :first_appointment_date, DateTime
+      attribute :emergency_contact_info_name, String
+      attribute :emergency_contact_info_relationship, String
+      attribute :emergency_contact_info_phone, String
+      attribute :emergency_contact_info_email, String
 
       def name
         "#{first_name} #{last_name}"
diff --git a/lib/mindbody-api/models/visit.rb b/lib/mindbody-api/models/visit.rb
index c8edc91..b7f4827 100644
--- a/lib/mindbody-api/models/visit.rb
+++ b/lib/mindbody-api/models/visit.rb
@@ -12,6 +12,7 @@ class Visit < Base
       attribute :web_signup, Boolean
       attribute :signed_in, Boolean
       attribute :make_up, Boolean
+      attribute :late_cancelled, Boolean
       attribute :service, ClientService
     end
   end
diff --git a/lib/mindbody-api/models/waitlist_entry.rb b/lib/mindbody-api/models/waitlist_entry.rb
new file mode 100644
index 0000000..8a6cb13
--- /dev/null
+++ b/lib/mindbody-api/models/waitlist_entry.rb
@@ -0,0 +1,11 @@
+module MindBody
+  module Models
+    class WaitlistEntry < Base
+      attribute :id, Integer
+      attribute :class_id, Integer
+      attribute :class_date, DateTime
+      attribute :client, Client
+      attribute :class_schedule, ClassSchedule
+    end
+  end
+end
\ No newline at end of file
diff --git a/lib/mindbody-api/response.rb b/lib/mindbody-api/response.rb
index 8157c6c..559141e 100644
--- a/lib/mindbody-api/response.rb
+++ b/lib/mindbody-api/response.rb
@@ -67,9 +67,11 @@ def normalize_hash(hash)
             hash[key] = normalize_hash(value)
 
             key_singular = map_key(key).singularize.to_sym
+            key_plural = key.to_s.pluralize.to_sym
 
             if value.has_key?(key_singular)
-              hash[key] = value[key_singular]
+              val = value[key_singular]
+              hash[key] = (val.is_a?(Array)) ? val : [val]
             elsif value.has_key?(:string)
               hash[key] = value[:string]
             elsif value.has_key?(:int)
diff --git a/lib/mindbody-api/services/class_service.rb b/lib/mindbody-api/services/class_service.rb
index 63ffbaf..170a5b9 100644
--- a/lib/mindbody-api/services/class_service.rb
+++ b/lib/mindbody-api/services/class_service.rb
@@ -4,9 +4,12 @@ class ClassService < Service
       service "ClassService"
 
       operation :get_classes
-      operation :get_class_visits,           required:[:class_id]
+      operation :get_class_visits,             required:[:class_id]
       operation :get_class_descriptions
       operation :get_class_schedules
+      operation :get_waitlist_entries,         required: [:class_ids]
+      operation :add_clients_to_classes,       required: [:class_ids, :client_ids]
+      operation :remove_clients_from_classes,  required: [:class_ids, :client_ids]
     end
   end
 end
diff --git a/lib/mindbody-api/services/sale_service.rb b/lib/mindbody-api/services/sale_service.rb
index 50e7c05..b5beeea 100644
--- a/lib/mindbody-api/services/sale_service.rb
+++ b/lib/mindbody-api/services/sale_service.rb
@@ -5,6 +5,7 @@ class SaleService < Service
 
       operation :get_accepted_card_type,      :locals => false
       operation :get_sales
+      operation :checkout_shopping_cart,      :required => [:client_id, :cart_items, :payments]
       operation :get_services
       operation :get_packages
       operation :get_products
diff --git a/mindbody-api.gemspec b/mindbody-api.gemspec
index 4d3a621..2cde5e3 100644
--- a/mindbody-api.gemspec
+++ b/mindbody-api.gemspec
@@ -26,4 +26,5 @@ Gem::Specification.new do |gem|
   gem.add_development_dependency 'simplecov', '~> 0.8.2'
   gem.add_development_dependency 'guard-rspec', '~> 4.2.8'
   gem.add_development_dependency 'rake', '~> 10.0.3'
+  gem.add_development_dependency 'pry'
 end
diff --git a/spec/client_spec.rb b/spec/client_spec.rb
index e6e22de..a0be5ce 100644
--- a/spec/client_spec.rb
+++ b/spec/client_spec.rb
@@ -7,6 +7,11 @@
     creds.stub(:source_name).and_return('test')
     creds.stub(:source_key).and_return('test_key')
     creds.stub(:site_ids).and_return([-99])
+    creds.stub(:open_timeout).and_return(nil)
+    creds.stub(:read_timeout).and_return(nil)
+    creds.stub(:username).and_return(nil)
+    creds.stub(:password).and_return(nil)
+    creds.stub(:prod_mode).and_return(true)
     MindBody.stub(:configuration).and_return(creds)
     @client = MindBody::Services::Client.new(:wsdl => 'spec/fixtures/wsdl/geotrust.wsdl')
 
@@ -30,6 +35,58 @@
                                    }
                                 }}}
     end
+
+    # We use #send here because `auth_params` is a private method and when
+    # adding this functionality I didn't want to change the public API contract.
+    # This should be considered an external-facing unit test as calls to
+    # {#call} now respect `auth:` alongside `:message`.
+    describe " (when using `auth:`)" do
+      it 'should inject MindBody.configuration values for the nil case' do
+        ret = subject.send(:auth_params, nil)
+
+        expect(ret["SourceCredentials"]["SourceName"]).to eq('test')
+        expect(ret["SourceCredentials"]["Password"]).to eq('test_key')
+        expect(ret["SourceCredentials"]["SiteIDs"]["int"]).to eq([-99])
+        expect(ret["UserCredentials"]).to be_nil
+      end
+
+      it 'should defer to passed-in values when provided' do
+        auth = {
+          :source_name => "override_name",
+          :source_key => "override_key",
+          :site_ids => [ -105 ]
+        }
+
+        ret = subject.send(:auth_params, auth)
+
+        expect(ret["SourceCredentials"]["SourceName"]).to eq('override_name')
+        expect(ret["SourceCredentials"]["Password"]).to eq('override_key')
+        expect(ret["SourceCredentials"]["SiteIDs"]["int"]).to eq([-105])
+        expect(ret["UserCredentials"]).to be_nil
+      end
+
+      it 'should inject UserCredentials when provided' do
+        auth = {
+          :source_name => "override_name",
+          :source_key => "override_key",
+
+          :username => "override_user",
+          :password => "override_pass",
+
+          :site_ids => [ -105 ]
+        }
+
+        ret = subject.send(:auth_params, auth)
+
+        expect(ret["SourceCredentials"]["SourceName"]).to eq('override_name')
+        expect(ret["SourceCredentials"]["Password"]).to eq('override_key')
+        expect(ret["SourceCredentials"]["SiteIDs"]["int"]).to eq([-105])
+        expect(ret["UserCredentials"]["Username"]).to eq('override_user')
+        expect(ret["UserCredentials"]["Password"]).to eq('override_pass')
+        expect(ret["UserCredentials"]["SiteIDs"]["int"]).to eq([-105])
+      end
+    end
+
     it 'should inject the auth params' do
       Savon::Operation.any_instance.should_receive(:call).once.with(@locals)
       subject.call(:hello)
diff --git a/spec/service_spec.rb b/spec/service_spec.rb
index fe88b38..38ae890 100644
--- a/spec/service_spec.rb
+++ b/spec/service_spec.rb
@@ -30,11 +30,18 @@
           MindBody::Services::Service.operation :test
         end
 
-        it { should respond_to(:test) }
-        its(:new) { should respond_to(:test) }
+        it do
+          should respond_to(:test)
+          should respond_to(:test_with_auth)
+        end
+        its(:new) do
+          should respond_to(:test)
+          should respond_to(:test_with_auth)
+        end
 
         it 'should have optional locals' do
           expect(subject.method(:test).arity).to eql(-1)
+          expect(subject.method(:test_with_auth).arity).to eql(-2)
         end
 
         it 'should delegate to the class method' do
@@ -42,8 +49,10 @@
           locals = {:foo => :bar}
 
           subject.should_receive(:test).with(locals).once
-
           instance.test(locals)
+
+          subject.should_receive(:test_with_auth).with({}, locals).once
+          instance.test_with_auth({}, locals)
         end
       end
 
@@ -52,11 +61,18 @@
           MindBody::Services::Service.operation :test_required, :required => [:foo, :bar]
         end
 
-        it { should respond_to(:test_required) }
-        its(:new) { should respond_to(:test_required) }
+        it do
+          should respond_to(:test_required)
+          should respond_to(:test_required_with_auth)
+        end
+        its(:new) do
+          should respond_to(:test_required)
+          should respond_to(:test_required_with_auth)
+        end
 
         it 'should have two required params and optional locals' do
           expect(subject.method(:test_required).arity).to eql(-3)
+          expect(subject.method(:test_required_with_auth).arity).to eql(-4)
         end
 
         it 'should delegate to the class method' do
@@ -64,11 +80,14 @@
           locals = {:foo => :bar}
 
           subject.should_receive(:test_required).with(:foo, :bar, locals).once
-
           instance.test_required(:foo, :bar, locals)
+
+          subject.should_receive(:test_required_with_auth).with({}, :foo, :bar, locals).once
+          instance.test_required_with_auth({}, :foo, :bar, locals)
         end
 
         it 'should require two params' do
+          expect{subject.send(:test_required_with_auth, {})}.to raise_error(ArgumentError)
           expect{subject.send(:test_required)}.to raise_error(ArgumentError)
         end
       end
@@ -83,21 +102,26 @@
 
         it 'should have two required params and optional locals' do
           expect(subject.method(:test_no_locals).arity).to eql(2)
+          expect(subject.method(:test_no_locals_with_auth).arity).to eql(3)
         end
 
         it 'should delegate to the class method' do
           instance = subject.new
 
           subject.should_receive(:test_no_locals).with(:foo, :bar).once
-
           instance.test_no_locals(:foo, :bar)
+
+          subject.should_receive(:test_no_locals_with_auth).with({}, :foo, :bar).once
+          instance.test_no_locals_with_auth({}, :foo, :bar)
         end
 
         it 'should require two params' do
+          expect{subject.send(:test_no_locals_with_auth, {})}.to raise_error(ArgumentError)
           expect{subject.send(:test_no_locals)}.to raise_error(ArgumentError)
         end
 
         it 'should not allow locals' do
+          expect{subject.send(:test_no_locals_with_auth, {}, :foo, :bar, :foobar => 'foobar')}.to raise_error(ArgumentError)
           expect{subject.send(:test_no_locals, :foo, :bar, :foobar => 'foobar')}.to raise_error(ArgumentError)
         end
       end