Incredible for a free app
It's great. If a device is lost, you get reports every 10 mins (2 if you pay premium), which are very detailed and useful if the police need help. You also have access to a painfully powerful alarm, that will scare the living hell out of any thief. The issues: It always has to be on in the background, and getting a connection for the updates is never certain. You also get emails from Prey consistently when it goes missing, so if your phone has email notifications on, the thief will realize you're tracking them. In conclusion it is amazing, despite the issues, for free app with an optional paid premium. It's the best I have seen so far, and I am very happy with it.
