WhatsApp Messenger app for iPhone is available free for download for a limited time period whereas normally its cost $0.99.
WhatsApp Messenger is a cross-platform smartphone messenger currently available for iPhone and other smartphones. The application utilizes push notifications to instantly get messages from friends, colleagues and family. Switch from SMS to exchange messages, pictures, audio notes and video messages with WhatsApp users at no cost. All features are included without the need for extra in-application purchase.
Download WhatsApp Messenger for iPhone