Today Viber announced that the new version 2.1.3 for Android is available at Android Market. Main feature is that Viber from now on can work on Android 4 devices.
Here is the original announment:
In addition, this version includes significant enhancements to the Viber voice engine, featuring better quality, improved support for low end devices and better handling of poor network conditions.
Viber is committed to the Android platform and has seen rapid growth on the OS over the last seven months since it first released the Android version of its app. Additionally, Viber offers Android users several unique features that aren’t available on the iOS version of the app.
Viber recently announced that over 50 million people have registered for the service. Each month, Viber users make over a billion minutes worth of calls and send close to a billion messages. Android users are playing an increasing role in this growth.



