In addition to the new version of Android being released today, well actually announced. Google is also launching a new release of Google Play Services. This one is version 4.0 and includes the Google Mobile Ads SDK, and offers plenty of improvements to geofencing, Google+, and Google Wallet Instand Buy APIs.
Google is boasting that over 97% of Android devices are running Gingerbread of higher now, and that they are now dropping support for Froyo starting with Play Services 4.0. This is in an effort to offer more powerful APIs in the future. Which basically means for developers that they won't be able to utilize those new APIs on devices running Android 2.2 and lower. As usual with Google updates, this one is rolling out slowly across he globe. But you can download the latest SDK and start developing with the new APIs now, with the new KitKat emulator.
One of the new features in the new Google Play Services includes Google Mobile ads. If you're one of those developers that's using Admob to make some income from your app, the new Google Mobile Ads SDK in Google Play Services helps provide seamless improvements to you users. This helps with things like bug fixes, which can be pushed out automatically without you having to do anything.
There have also been some changes to Maps and Geofencing APIs, since launching in Google Play Services 3.1. You can now save power by requesting larger latency values for notifications alerting your app to users entering or exiting geofences, as well as a request that entry alerts are sent only after a user stays within a geofence.
There have also been changes to Google+ and Google Wallet Instant Buy. Now apps that use Google Sign-In will be updated with a more simplified sign-in consent dialog. Additionally, Google Wallet Instant buy APIs are now available for everyone to try out within a sandbox, with a simplified API that streamlines the buy-flow and reduces integration time.
Finally, there's also some new user control over advertising identifier. Which is to give users better controls and to provide you with a simple, standard system to continue to monetize your apps, this update contains a new anonymous identifier for advertising purposes. Google Settings also includes user controls that enable users to reset this identifier, or opt out of interest-based ads for Google Play Apps.
Lots of changes in Google Play Services 4.0, and I'm sure plenty more will be found once someone tears down the APK when it begins rolling out.