They should make a device to prevent soda machines from falling on people when they try to knock it over. You see, more people die from that every year then shark attacks. So it doesn't matter if the device works or not, the real question is DO WE REALLY NEED SOMETHING LIKE THIS? I believe it is all a scam created to scare people into buying something. The danger of a shark attack is EXTREMELY minimal, and the money invested in this technology is a waste of resources. It would be better if that time and money was put to use in saving sharks, not defending ourselves against a non existent threat.