WhatsApp Messenger is a smart phone messenger offered for Android, BlackBerry, iPhone, Windows Phone and Nokia phones. It uses WiFi or 3G to message with family and friends and can receive and send pictures, audio notes, messages and video messages. Group chats are also possible.
It is FREE for First year and they may charge $1.99/year. This allows you to send millions of messages of any kind per day because it uses 3G/EDGE or Wi-Fi with out getting logged in as like any other conventional computer devices and other added assert is that if you go offline , this app will save your messages offline until you come again to use.
Apart from this allows you to Exchange contacts, Custom notification sounds, Landscape mode, Broadcast messages ,Precise message time stamps, Email chat history, Custom wallpaper, Share location and so enjoy it.