Google started its I/O conference with a focus on APIs for Android, a way to underscore that this is a developer conference after all. But the first real announcement is the Google Play game services.
This new service makes it possible to save game status in the cloud not only across devices, i.e. a phone and tablet, but across platforms as well, meaning the web as well as native apps.
There's more though, the game services will provide achievements for any app, as well as a leaderboard. All of this is based on Google+, of course, so you can compete with your friends.
The game services should make it a lot easier for games to add features like social multiplayer or cloud saves, things that are out of the reach of smaller developers.