Viber rocks in VOIP

Viber is a new arrival in VOIP service. It is a proprietary cross-platform instant messaging  Voice-Over-Internet Protocol application for smartphones developed by Viber Media. In addition to text messaging, users can exchange images, video and audio media messages. The client software is available for Windows, Mac OS, Android, BlackBerry OS, iOS, Series 40, Symbian, Bada, Windows Phone, Mac OS X and Microsoft Windows. Viber works on both 3G and WiFi networks.

Viber reached 200 million users as of May 7, 2013.

History
Viber was initially launched for iPhone on Dec 2 2010, in direct competition with Skype. A pre-release version for Android appeared in May 2011 but was restricted to 50,000 users; an unrestricted version was released on July 19, 2012. Viber for BlackBerry and Windows Phone devices were launched on May 8, 2012. On reaching 90 million users on July 24, 2012, group messaging service and HD Voice engine were added to both Android and iPhone applications.
Applications for Nokia's Series 40, Symbian and Samsung's Bada platform were also announced on the same day. Initially, the voice calling feature was only available for iPhone and Android applications, with a promise that voice would be added in upcoming versions for Bada, Symbian and Windows Phone applications, with no mention of either Series 40 or Blackberry OS.
The limitation seems to lie in core of Blackberry OS and Series 40 which does not have easy support for VoIP apps. As promised, on Sept. 22 2012 HD quality phone calls and hold group-messaging sessions were made available for Windows phone but only for Nokia users, as part of exclusive partnership with Nokia. Viber with voice was officially released for all Windows Phone 8 devices on April 2, 2013.

Features & Functionality
The actual functionality varies from platform to platform with iOS and Android being the first to receive new features. Viber includes text, picture and video messaging across all platforms, with voice calling available only to iPhone, Android and Nokia's Windows Phone although HD voice is planned for Windows Phone 8.
The application's user interface includes tab bar on the bottom giving access to messages, recent calls, contact, the keypad and a button for accessing more options. Upon installation, it creates a user account using one's phone number as username.
Viber synchronizes with the phone's address book, so users do not need to add contacts in a separate book. Since all users are registered with their phone number, the software returns all Viber users among one's contacts. The newest version of Viber (Version 2.3) has added smileys and other default images.

Languages and localization
Viber is currently available in 30 languages and locales: English, Arabic, Albanian, Traditional Chinese, Simplified Chinese, French, Farsi, German, Italian, Spanish, Russian, Hebrew and Portuguese.

Company
Viber Media is a Cyprus-based company with development centers in Belarus and Israel. The company was founded by American-Israeli entrepreneur Talmon Marco.
The company currently does not generate revenues, but announced it would start generating revenues in 2013 via a "sticker store". The company is funded by individual investors. As of May 2013, $20M was invested in the company.