For the mainnet version, you need to become tester (see https://plus.google.com/101256420499771441772/posts/VhyWchXkBFR). The testnet version is on Google Play already for everyone. There is also direct downloads here: https://github.com/schildbach/bitcoin-wallet/releases/tag/v4.0
Here is what's new in v4.0:
- All Bitcoin addresses are now deterministically derived from one single secret, which was created when you installed the app for the first time. So from now on, only one backup is needed to recover all your future funds in that wallet.
- The app does its best to not reuse addresses any more. "Request coins" will use a fresh address on each invocation. The current address in the QR code on the main page changes as soon as coins are received on it.
- When sending coins, the fee is shown while you type and before you press "Send". After sending, you'll see the paid fee in the transaction list.
- When sending coins, most errors are now shown already before you press Send.
- The app now requires Android 4.0.3 or higher. This makes UI development much easier in future.
- The app has a fresher, sharper looking app icon. The icon for the testnet version is now entirely grey.
- On Android 4.1 or higher, the app-widget is now horizontally resizable.
- Based on bitcoinj 0.12.
Thanks to everyone participating, especially to all of the bitcoinj team members and the busy translators on Transifex!