WhatsApp Messenger is a cross-platform mobile messaging app which allows users to exchange messages without having to pay for SMS. WhatsApp Messenger is available for iPhone, Blackberry, Android, Windows Phone, Nokia, and Symbian platforms.
Since WhatsApp Messenger uses the same internet data plan that subscribers use for email and web browsing, there is no cost to message and allows them to stay in touch with their friends.
In addition to basic messaging WhatsApp users can create groups, send each other unlimited images, video, and audio media messages.
Founders: Brian Acton, Jan Koum