Frank, the wireless motor kill switch has been around for quite some time.
See
this thread, nearly two years old. You made a contribution to that one.
In any case, this is only a minor improvement over the standard motor cutoff lanyard.
The question for singlehanded sailing, as opposed to motoring, has never been quite that simple.
Saying "build in some weather helm" doesn't work, because the autopilot will defeat it. You can't even just shut off the autopilot, since for every autopilot with which I'm familiar, that will simply lock the wheel, but still permit the boat to continue to sail away from you for who knows how far.
The real question is how to disconnect the autopilot, and then, regardless of wind, weather, current and point of sail, cause the boat to execute some maneuver which will stop it so you have a chance to swim to it (or pull yourself to it by your tether) and climb back aboard.