Originally Posted by caltexflanc
You will want something that can be submerged in salt water. There are a variety on the market, most designed for commercial crew use. But I recall Raymarine having one for instance: Raymarine LifeTag
I spend much of my time on the boat alone, I have a Raymarine Lifetag system installed, it sounds an alarm if I go overboard. The alarm circuit also powers a relay that halts power to the fuel solenoid on my engine shutting it down. Last thing I want to watch from the water is the boat cruising off on auto pilot!