I cannot remember what the product is called, but there was someone who invented an alarm that went off when a certain snap on the boat cover was opened. This was a while ago, but search for boat alarms, or something similar on here. We had our stereo stolen last year, unfortunately, for the price of the head unit, it is not even worth filing a claim. The night we got taken, they hit about 6 boats all moored out within a couple hundred feet of each other. I wish I would have been down there with a bat to see them jump on my boat.