I saw a program that does something like this, lojack style, for the iphone the other day... lemme see if i can find the article...

http://www.tuaw.com/2008/02/21/tuaw-responds-iphone-lojack/

haha... not super accurate and not really what you want, but fun none the less.

Or howabout this:
http://www.itzcomm.com/SPOT/SatelliteTrackers.html