Prey Anti-Theft is a security app that lets you track and (hopefully) find your lost or stolen phone.
Losing a phone isn't just a pain, it can be a huge security risk. People have photos, passwords, and all kinds of personal information on their phone nowadays. Prey Anti-Theft gives you peace of mind by letting you lock down and locate your phone if it ever becomes lost or stolen.
To activate Prey Anti-Theft, you have to navigate to the Prey website and mark your phone as "missing." You can then see where your phone is, its IP, and other useful information. You can then remotely lock the phone, sound an alarm, and put a message up on the screen. iOS users can also put up a fake message on the screen to get the thief to look at the front facing camera while Prey Anti-Theft snaps a photo.
Overall, Prey Anti-Theft is a great application for basic anti-theft measures but is limited by Apple's developer restrictions for apps running in the background.