Google+ team just released a new feature called Google+ sign-in (aka application sign-in).
This allows website and mobile app developers to easily and painlessly integrate google account sign-in into their apps by just including few lines of code and allows 500 million+ google+ users to socially engage in your website or apps.
What is Google+ sign? This short video explains it quickly
Here is the blog post about the announcement.
You don’t have to create another account or remember another password. Just use your Google+ account to sign-in into any website or app that support Google+ sign-in.
TheFancy.com, Fitbit.com are some of the sites that already support Google+ sign-in. Just click on the sign-up link in these sites and you’ll find Google+ sign-in as one of the options.
Google+ has also added a Manage Apps section available under https://plus.google.com/apps that allows to change permissions you have given to any website or apps. You can find all your application activities (website or mobile apps) appear under the app activities tab.