The major enhancement in the latest version of Google Play Services is the inclusion of the Mobile Ads SDK and there are also to improvements to geofencing, Google+, and Google Wallet Instant Buy APIs. It also marks the end of an era with discontinuation of Froyo support.

At the same time as releasing KitKat - see Android 4.4 KitKat The Programmers Take, Google rolled out Play Services 4.0 which now includes the new Google Mobile Ads SDK.

Not only does this SDK let you monetize your apps and connect with over a million Google advertisers, its inclusion  in Google Play services brings the advantage of "seamless auto-updates" with bug fixes, for example, being pushed out automatically to users. This update also contains a new, anonymous identifier for advertising purposes (to be used in place of Android ID). Google Settings now includes user controls that enable users to reset this identifier, or opt out of interest-based ads for Google Play apps.

The Maps and Geofencing APIs that launched in May have been updated to improve overall battery efficiency and responsiveness and the Maps API enhances map customization features, letting you specify marker opacity, fade-in effects, and visibility of 3D buildings. It’s also now possible to change ground overlay images.

With the Google Play 4.0 apps that are enabled with Google+ Sign-In will be updated with a simplified sign-in consent dialog and Google Wallet Instant Buy APIs have been streamlined to reduce integration time and can now be tried out within a sandbox. Google Wallet Instant Buy also includes new Wallet Objects, which means you can award loyalty points to a user's saved rewards program ID for each applicable purchase.

But Google Play Service 4.0 is going to upset anyone who is still supporting Android 2.2. The blog announcement states:

With over 97% of devices now running Android 2.3 (Gingerbread) or newer platform versions, we’re dropping support for Froyo from this release of the Google Play services SDK in order to make it possible to offer more powerful APIs in the future. That means you will not be able to utilize these new APIs on devices running Android 2.2 (Froyo).

So an unhappy day for some - 3% of Android users is still a pretty large number of users!