JustAssembly is a free open source project. You can easily:

Add the functionality that you need and want
Share features and solutions with the larger community so everyone benefits
Leverage contributed fixes and additions
See the source code and verify for yourself what the code does
Study the code and learn from the best

The Google Integrator makes it easy to access Google Apps and Services from any supported platform or development technology. The easy-to-use components can be used to connect applications to Google cloud storage, and to easily integrate connectivity with popular Google Apps like Google Docs, Google Calendar, and Gmail Contacts. Leverage always-on access to Google Apps and Cloud services. Google Integrator provides easy-to-use components for accessing Google Services including Google Storage, Google Docs, Google Calendar, Gmail Contacts, and more!

Xamarin apps are built with standard, native user interface controls. Apps not only look the way the end user expects, they behave that way too. Xamarin apps have access to the full spectrum of functionality exposed by the underlying platform and device, including platform-specific capabilities like iBeacons and Android Fragments. Xamarin apps leverage platform-specific hardware acceleration, and are compiled for native performance. This can’t be achieved with solutions that interpret code at runtime.