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.
The Google+ Android API allows you to integrate sign-in and social features into your app.
Key Developer Features
Trusted authentication
  Google+ Sign-In is a simple, trusted, and secure way to let people sign in to your app with their
  Google credentials and bring along their Google+ info.
  Add
  sign-in.
Access the profile and social graph
  Once users have signed in with Google, your app can welcome them by name, display their picture,
  connect them with friends, and lots more.
  Access the
  social graph.
Stand out in the stream
  Interactive posts is a rich way of sharing to Google+. It lets users prompt friends to take
  specific actions in your app from a Google+ post, like "listen," "RSVP," "check-in," and over 100
  more actions.
  Post
  interactive content.
Recommend content
  Add a native +1 button so users can recommend content from your app. These endorsements can give
  your app more credibility and help it grow faster.
  Add the
  +1 button.
Get Started
The Google+ Android APIs are part of the Google Play services platform. To use Google+ features, set up the Google Play services SDK in your app development project. For more information, see the Getting Started guide for the Google+ Platform for Android