The latest laptop-recovery application is a kind of mash-up, using several systems to provide information about a laptop's location and who's currently using it. GadgetTrak's new MacTrak ($59.95, one-time fee) uses Skyhook Wireless's Wi-Fi Positioning System, the same technology that's part of how the iPhone and iPod touch determine location. MacTrak also uses Flickr as a way to post photos snapped of someone using a machine identified as lost or stolen.

There are already several programs available that let you install software that's regularly checking for an activation signal to leap into action if your laptop is marked (in various ways) as being out of your hands. For a full rundown, see "Help! I'm Being Held Captive, and All I Have Is a Wi-Fi Network!," 2008-05-03.

But MacTrak appears to have - or at least disclose - the most accurate way to track a missing computer. Skyhook's WPS relies on being in areas that have enough Wi-Fi signals to pinpoint a location, and on having an active network over which to perform queries. It's likely that a stolen laptop would wind up on a network in a city, unless thieves are becoming savvy and keeping computers locked down.

MacTrak also uniquely transmits collected information directly to you, uploading it to Flickr (if you have an account set up, which is free for limited uploads), and sending via email. GadgetTrak says they don't run a monitoring center but will help connect users with law enforcement if asked.

I'd love to see the face of a police officer, used to dealing with unrecoverable machines, when you walk in with a picture of the thief, a set of GPS coordinates with a map, and information about the network on which the thief connected.