WhatsApp Messenger is a smartphone messenger available for iPhone and other smartphones. WhatsApp uses your 3G or WiFi (when available) to message with friends and family. Switch from SMS to WhatsApp to send and receive messages, pictures, audio notes, and video messages. First year FREE! ($0.99 USD/year after)
* NO HIDDEN COST: Once you and your friends download the application, you can use it to chat as much as you want. Send a million messages a day to your friends for free! WhatsApp uses your Internet connection: 3G/EDGE or Wi-Fi when available.