Viber comes with some exciting features,Viber's cutting edge Technology ensures a good HD sound quality. The sound quality is better than any regular calls made from a GSM phone.Also the App runs in the background without draining much of battery.
Viber creates usernames and build new list instantaneously by synchronizing with your mobile phone no and contact list to show who has Viber already. All features are 100% free requiring no additional application to make calls or messages.
click here to go to Viber
(sources: Viber)