Although I have a Tracker Horizon fitted I don't rate these devices much. Most of their success seems to ride on the fact that the insurance companies insist on you having one so my two penneth worth is NavTrak seem to have the edge on dealing with today's car theft ie. the system still detects theft even when the keys have been stolen - tracker does not as they still have to be alerted. I too have switched to Liverpool and Victoria and they also confirmed that they will insure an M3 without a tracking device and they definitely offer top cover at the lowest prices. Hope that helps.