While it may not have been one of the most talked-about announcements from Google I/O, the Google+ History API could end up being one of the most significant for the company. It's been described as Google+'s answer to Facebook's frictionless sharing, and that could certainly be significant for third-party apps.
As my colleague Zach Walton explained last week, it collects everything users have done with apps, connected to Google+, and adds it to their personal pages for sharing at the user's discretion. Essentially, it operates like Google+'s Instant Upload photo feature, but for other app activities.
Google has posted a video from a Google I/O session, discussing the API, and how to use it.
"Google+ history presents new opportunities to increase traffic to your site and engagement with your content by allowing users to connect their Google profile to your site," explains Google. "This session will explore the value of Google+ history and review basic implementation. Special guests will be on hand to describe their early success with this new service."
As an added bonus, here's the fireside chat with the Google+ platform team from Google I/O: