Apple Inc. (NASDAQ:AAPL) has released an application called Find My iPhone as a free download. If you lose your iPad or iPhone, you can install the Find My iPhone app on any other iPhone, iPod Touch, or iPad to find out where you left it.
You have to sign in with your iTunes member name and password to locate the missing device on a map. A message will be displayed or played on the device too.
Through the Find My iPhone app, you can also wipe out data or lock the missing Apple device. You can download it here: [iTunes Link]