The beta version of the app does allow you to send text and picture messages, which, depending on your operator contract, may help you cut costs, especially when roaming. It is comparable to other messaging type applications (e.g. Palringo), but Viber emphasises ease of use, integration (e.g. there are no friend requests, instead Viber will also automatically look up other users by matching existing phone numbers in your contacts) and has a large established user base of 70 million users (it has added 20 million since February).
To get around the limitations of not being able to run in the background Viber uses push notifications to alert user to incoming messages and plans to do the same for incoming calls, once that functionality has been added to the app.
100% free: Viber and all our features are completely free, with no subscriptions or purchases. Avoid mobile phone “bill shock” – text other users, on any network, as much as you want. All you need is a 3G or Wi-Fi Internet connection, and friends who get Viber too!Simple to use: Viber just works, and lets you connect with your friends whose numbers you already have. It synchs with your mobile phone number and contact list to instantly show who already has Viber. Never again must you seek out your own contacts, create new usernames, or build new lists.
Viber can be downloaded from the Windows Phone Marketplace for free.