> Of course, you'd have to find a way of guarding against malicious entries.

The system is operated in conjunction with the police. Stolen systems are required to have a police report number.

Doesn't go by MAC address, but similar idea: http://www.orbicule.com/undercover/

Orbicule's Undercover coordinates with police, built-in phone-home software, a Mac's built-in camera, etc. Nifty stuff.

This idea would work really well if you implemented it in wireless access points since they are already listening for Probe Request packets from stations that aren't associated to their network.

This means that if anybody opens a stolen laptop in the vicinity of one of these APs it would be detected without requiring that the laptop be associated to the local network.

I think there's a big problem with this. Where it'd be useful is at large organizations, which generally create multiple subnets to structure their network. This would mean that you need to put this client in the router, or force the organization to have an always on box for each subnet with the client.

MAC address can be changed.

99.999% of people who steal hardware aren't smart enough to do this. Also, 99.9999999% of people who use stolen hardware have bought it (off eBay for instance) and won't scrub it, but will plug it in somewhere that's monitoring.

I think this is a really good idea.