One glaring omission from Google+ was the lack of third-party app support, preventing you from sharing activity from certain apps and more. Today Google released sign-in for Google+ so developers can offer greater options.

Google+ Sign-In must be integrated by developers, so currently you'll only find it in a few apps like OpenTable, Fitbit, Flixter, and Shazam. That said, other integrations are underway and hopefully we should see additional options in the near future. Google took awhile getting this feature ready because they didn't want to allow third-party apps to cause "social spam," or the constant stream of pointless information you often find in the news feeds of your Facebook friends. Additionally, Google gives you a lot of control over how apps can interact with your account and you can adjust the settings to your liking. Just visit this page to keep an eye on any apps active on your account to keep the working the way you want.

Introducing Google+ Sign-In: simple and secure, minus the social spam | Google+