For a shut off capability, I've seen a lanyard attached to a riders wrist on snowmobiles, and personal watercraft, and if the operator and vehicle part ways in some sort of 'incident', the lanyard pulls a pin out of a switch, and kills the ignition .
Don't know of any motorcycle, or ATV that have the same capabilities .
For your lack of memory of the 'incident' like I have said before, I was involved in a 'crash' on my first motorcycle, a '79 Yamaha XS 400, 29 years ago yesterday .
I missed a turn off, hit the brakes hard, also had a friction lock on the throttle set .
All I remember, is hitting the brakes, then the next thing I remember, is sliding to a stop on the right side of the bike, with my hands still on the hand grips, and feet still on the foot pegs .
No memory of about 5-6 seconds what so ever .