Beta GSM mobile phone tracking system via the GPS-TRACK satellite network
You plug in a cell phone number and it shows you where the phone is on a map.
According to the website:
Based on repeater triangulation, the system tracks mobile phones using GPS and GSM technology
Approximate margin of error:
10 meters (max.) for mobile phones in Europe and the U.K.
25 meters (max.) for mobile phones in the U.S.A., South America and Canada.
50 meters (max.) for mobile phones elsewhere.
This system will not work in countries without GSM technology networks.