WhatsApp Messenger for Android

WhatsApp Messenger is a smartphone messaging app which allows you to exchange messages with your friends and contacts without having to pay for SMS. To send and receive messages, WhatsApp utilizes your existing smartphone internet data plan: 3G/EDGE (or Wi-Fi when available).
WhatsApp only works among users who have the application, so after you download WhatsApp, make sure to use the "Tell a Friend" feature to share this App with the friends and contacts in your address book.