Wickr is a free app for the iPhone that allows you to send self-destructing, private instant messages to your friends. You can send text messages, video and audio messages. The whole transmission process is private — even the Wickr app developers cannot read the message, because they are encrypted before they leave your device.
Wickr also has a feature that purges any lingering traces of your messages in the phone’s memory and logs. An Android version of Wickr is said to be coming soon.