That's a good point.
It wouldn't be that difficult to fashion a system using a garage door opening system or an inexpensive radio-control toy whereby a person could attach a small transmitter to themselves which could be used in such an emergency to de-activate an autopilot system.
It would probably be less trouble to create than to swim nine miles to shore.
I think making this waterproof against salt water immersion would be difficult, but possible.
Cost might be high.
Monday Morning Quarterback?