I am using the SM services electronic kill switch. It seems to work well, if the receiver loses power the engine cuts and won't start if it is not switched on. I am going to reprogramme mine I think so the kill switch only works when the throttle is all the way down so i can't accidentally shut it off in-flight. When I used to use the throttle as the channel on my kill switch you would notice a drop in revs if you accidentally hit the switch. I never did it in the air but there you go, I am just taking precutions.
good luck
Paul