Undercover can help you locate any lost or stolen iPhone or iPod.
Every time the Undercover application is launched, the phone’s location and IP information is stored in your web account. You can then login to your account to track the device.
Thanks to the clever use of push notifications, the latest version (1.5) even allows you to remotely launch Undercover on the stolen iPhone in order to track the thief’s location.
YouTube Video: http://www.youtube.com/watch?v=KwQsdl-D38o