Find my iPhone 1.0
If you lose your iPhone or iPad while on the go, simply install this free app on any other iPhone, iPad, or iPod touch to find it.
Sign in with your member name and password (MobileMe subscription required) to locate your missing device on a map and have it display a message or play a sound. You can even remotely lock the device to protect your privacy, or wipe it to permanently delete all of your data if you think that it wont be returned.
Compatible with iPhone, iPod touch, and iPad. Requires iOS 3.1.3 or later. MobileMe subscription required.