In May, Google announced Google Wallet – an app that allows you to tap and pay using near filed communication (NFC). Google has been working with Citi, MasterCard, Sprint and First Data to bring this app to Android users. Today, Google announced that they are releasing the first version of the app to Sprint and all Nexus S 4G customers on Sprint will receive the app through an over-the-air update.

Currently, Google Wallet only works with Citi MasterCard credit card and the Google Prepaid Card. However, Google says that they are working with Visa, Discover and American Express to bring their cards support to future versions of Google Wallet.

Google is giving all the early adopters a $10 free bonus, if they set up a Google Wallet account before the end of the year. Check out the demo video of Google Wallet in action below.

Also in Android news, Google is asking developers to get their apps Ice Cream Sandwich ready, in preparation for launch of the new mobile OS. Tim Bray posted on Android developers blog:

Although Honeycomb remains tablets-only, the upcoming Ice Cream Sandwich (ICS) release will support big screens, small screens, and everything in between. This is the way Android will stay from now on: the same version runs on all screen sizes.

Some Honeycomb apps assume that they’ll run only on a large screen, and have baked that into their designs. This assumption is currently true, but will become false with the arrival of ICS, because Android apps are forward-compatible — an app developed for Honeycomb is compatible with a device running ICS, which could be a tablet, a phone, or something else.

So, if you’ve developed a tablet app on Honeycomb, it’s important that your app do one of two things: prevent installation on smaller screens or (preferably) support smaller screens with the same APK.

Google has posted complete details on how the developers can get their apps ready for Ice Cream Sandwich with code showing what changes they need to make. You can get more information on Android Developers’ blog.