Pdelcast:
I would like to switch it off through the on/off switch by replacing the on/off switch with a remote controlled relay, the batteries will stay connected.
Arct1k:
I would like to have some completely independent means of shutting it down in case of a runaway or smoke/fire.
As far as I understand the 2.4Ghz technology a runaway should be completely impossible in theory, but it once happened to me with my Savage Flux and the supplied RTR 2.4Ghz Radio.
The car suddenly went on full throttle, hit my ankle and left a scar, did some flips, jumped down 10 stairs, hit a tree, landed on it's roof and stayed like that for maybe 5 seconds with tires balooning to 10 inch diameter, then got back on it's wheels because the tires were touching the ground again, did some backflips again and then the nightmare was suddenly over. I couldn't find out what the reason was as everything was working just normal after that. I'm quite happy that nobody was around, if somebody would have been near the stairs, he would probably have been hit in the face by the car.
After that I have thrown the HPI RTR radio away and replaced it with a Traxxas TQi RTR radio that never had a single glitch or any other problem so far, but I like to be on the safe side nevertheless.
Seeing a powerful brushless car going beserk is not something I want to repeat.