Autotether $295; 888/593-4181, www.autotether.com 4 Unlike traditional lanyard kill switches, this completely wireless device clips right into the ignition switch, allowing operator and passengers to move about freely. Should anyone fall overboard, the submerged sensor sends radio waves to a receiver connected to the boat's ignition, setting off an alarm. For added safety, a red alert button can also be pushed to kill the engine. The completely portable device can also be used to monitor watersport activities. Included in the kit is an ignition switch clip, one transmitter, two personal sensors, and two AAA batteries.