Have a slightly differant security setup with my RIB that although not as high Tech as GPS does give me some peace of mind (and was relativley cheap!)
I work with my laptop most of the day and so installed a $40.00 web cam to cover the side of the house. This way I can keep an eye on the boat.
To give an extra security measure, I installed a motion sensor by the gate to the boat and then connected it to a cheap auto-dialler from Tandy. That way when anyone is messing about there it pages me, so I can check the laptop and look who's around.
Worked well so far, and field tested when the electric meter man stopped by!
(Got ugly images of his rear bending over to read the meter!!
At least this way, no false alarms to the police, as you decide if there is a threat and when to call the cops,