As a 12 volt retailer and go fast boat owner I have been researching these since the first thread on this subject a few months ago. I have decided to carry the viper brand. Attached link covers the features of the unit and of course not all the features apply in a marine application but the tracking functions , geo fence, unauthorized movement, status check, low battery warning , battery tamper, and some other very good features for a marine app.

http://www.directed.com/security/vip...S_features.asp