With Google+ Sign-In, users can sign in to your Android, iOS and web apps using their existing Google credentials, and bring along their Google+ info for an upgraded experience. We already provide APKs and APIs that you can build directly into your apps. And today we're adding even more integration options.
Hundreds of thousands of developers already use the user management and social infrastructure platforms Janrain and Gigya to manage their sign-in systems. Today we're happy to announce that both companies are including Google+ Sign-In as part of their product suites!Google+ Adds More Ways To Sign In [googleplusplatform.blogspot.co.uk]