There are lots of theft-prevention tools for Android. One of the most highly praised is Lookout Security & Antivirus, a free app with a "find my phone" feature that will place the location of a lost phone on a Google Map. The service displays the device's last known location so even if the battery has died you might still get a trace. The software can also be set to record and email you a picture of anyone who attempts to unlock the phone, and it allows devices to be remotely wiped. As the name of the app implies, it also includes antivirus protection as well as the ability to back up and restore contacts, pictures and call history.