All APIs for communicating with the Android system.

Google Play services offers a standard authorization flow for all Google APIs and all components of Google Play services. In addition, you can leverage the authorization portion of the Google Play services SDK to gain authorization to services that are not yet supported in the Google Play services platform by using the access token to manually make API requests or using a client library provided by the service provider.

Google Cloud Messaging for Android (GCM) is a service that allows you to send data from your server to your users' Android-powered device, and also to receive messages from devices on the same connection. The GCM service handles all aspects of queueing of messages and delivery to the target Android application running on the target device. GCM is completely free no matter how big your messaging needs are, and there are no quotas.

A software library that allows for retrieving application state information.

Make your games social with Google Play game services. Add achievements, leaderboards, real-time multiplayer, and other popular features using the Google Play game services SDK. Let players sign in using their Google+ identities and share their gaming experience with friends. Visit developers.google.com/games/services for more information about integrating game services into your app.

Allow your users explore the world with rich maps provided by Google. Identify locations with custom markers, augment the map data with image overlays, embed one or more maps as fragments, and much more.

Google Play Services give your apps more features to attract users on a wider range of devices. With Google Play services, your app can take advantage of the latest, Google-powered features such as Maps, Google+, and more, with automatic platform updates distributed as an APK through the Google Play store. This makes it faster for your users to receive updates and easier for you to integrate the newest that Google has to offer.

The Google+ platform for Android lets you authenticate a user with the same credentials they use on Google every day. Once a user signs in with Google, you can create more engaging experiences and drive usage of your app.

SocialAuth is a Java library (.NET port & Android version available) for you if your web application requires: Authenticating users through external oAuth providers like Gmail, Hotmail, Yahoo, Twitter, Facebook, LinkedIn, Foursquare, MySpace, Salesforce, Yammer as well as through OpenID providers like myopenid.com. Easy user registration. All you need to do is create a page where users can click on buttons for the above providers or other supported providers. Just call SocialAuth and you can get all their profile details. Importing contacts from Google, Yahoo or Hotmail. Support for importing friends from Facebook, followers from Twitter and contacts from LinkedIn is available, but currently Facebook, Twitter and LinkedIn do not provide email addresses. UPDATE: Hotmail has stopped providing email addresses.

Paging indicator widgets compatible with the ViewPager from the Android Support Library and ActionBarSherlock. Originally based on Patrik Åkerfeldt's ViewFlow.