"Today we’re adding a new feature to the Google+ platform: application sign-in. Whether you’re building an app for Android, iOS or the web, users can now sign in to your app with Google, and bring along their Google+ info for an upgraded experience. It’s simple, it’s secure, and it prohibits social spam. And we’re just getting started." Read more on http://googleplusplatform.blogspot.fr/2013/02/google-plus-sign-in.html