Wikipedia
Trisent
Trisent Communications Ltd is a UK technology company headquartered in Dunfermline near Edinburgh. Trisent specialize in location-based services technology for locating and tracking mobile phones, vehicles and valuable assets. Trisent's core location technology is called Tri-cell which operates on GSM and 3G cellular networks. The important aspect of Tri-cell is that standard mobile phone handsets are used and no equipment is installed in the network.