OK - description of the "Tracker" device
"Tracker" is a brand and they have 3 types - there are other simular devices offered by different companies - but first I will try to explain tracker.
Tracker - A small unit is concealed in your car/boat. In standby mode this will draw very little current.
notice that your car/boat is missing you
ring tracker - they then activate your tracker device which starts sending out a signal that can be picked up by near by police cars. These police cars have 4 airials on the roof which can home in on the stolen car/boat - The device also send out an ID which is displayed in the police car which identifies the tracker unit - and hence what car they are looking for.
The problem with this system and boats is that its only activated after your call to Tracker. By the time you notice that your RIB is missing the T-leaf may have found the device and destroyed it.
Tracker Monitor - Same system as above, but the system itself detects unauthorised movements - signals to Tracker control and starts sending the signal.
With a car I assume that it is deactivated when you switch on the ignition - with a boat, if you don't de-activate it you will call the police each time you move the trailer!
Tracker Horizon - Same as Tracker Monitor - sets itself off automatically, but has a GPS inside and send its location to HQ. This info is then fed to the police
Costs are £199, £299, £499 + fitting +£99 per year - it does say on the web site that it can be fitted to a caravan/trailer
UK website here
ps The technology behind tracker I believe to be Motorola