In your design, did you consider RFID tags and an RFID receiver? Some of the RFID tags seem like they might have the range.
It might also be interesting to be able to trigger the GPS mob
function, and if the autopilot
is controllable, to put the he boat into the wind
, and/or cut the throttle. The phone
might not be able to do this, while other hardware
might have fewer issues.
Also, I am not sure that any of the class D radios can be remotely triggered to do a pan mob distress
call, but that might be useful as well.
The competition here are the mini-epirbs that are easy to keep in a pocket of your life jacket, if it has one. Arguably, triggering one of those if you fall in gets you strength from a lot of places and would be more useful if you were soloing... Unless you can automatically stop the boat.