Most of these apps have two things in common; they will attempt to locate the whereabouts of the computer and also send a picture of the thief using the built-in iSight camera. Now a new name has appeared in the field; hidden. The name is apt, since there's no visible sign on the computer that the software has been installed. There's no app in the applications folder, and no preference pane. To use the application, you simply download and install it, then restart your Mac.
Most of the time, your Mac won't be sending out updates of its location. When it is stolen or lost, you go to the hiddenapp.com website, log in, and then change the status for the tracked computer from "not stolen" to "stolen." The service begins looking for your Mac, and within minutes the site displays a Google map showing its approximate location (determined through Wi-Fi geolocation) and, more importantly, photos of the person using the Mac and screenshots of what they are doing. Location updates happen every 10 minutes and also include traceroute information including the public IP address of the Wi-Fi network being used by the thief. This information can be provided to ISPs and local police to help you get your computer back.