I've just bought one of these with a connection to my twin batt set up. Hopefully it will last for quite a while. It has a mic to listen in which could be a good laugh and be completely useless!!!
Anyway if you boat is stolen the phone companies can work out exactly where you are but this is not available to the public. You would have to rely on the police having the time and inclination to do this. (Unlikely!
Will let you know what its like when its in!!
PS dont tell anyone!!