Reply #87: The NASCAR guys have solved this

[Mopar151]

With the "Roush Interrupter"
CONCORD, N.C. -- Introduced in the fall of 2000, the Roush Ignition Interrupter System -- the only NASCAR approved automatic ignition interrupt system included in the 2002 NASCAR rulebook -- is now commonplace throughout NASCAR’s top three series.

The system is manufactured to shut off a racing engine system when the conditions of a "stuck throttle" exist, and has been track-tested for over 125,000 race miles with no documented component failures.

It works by sensing the intake manifold vacuum and the vehicle brake system pressure. The driver must only hit the brakes while the throttle is stuck for the system to shut down the engine ignition system.

The Roush Ignition Interrupter System includes two sensors that measure pressure inside the car. One sensor is located in the intake manifold, while the other is in the brake system. If the driver applies 1,100 psi (pounds her square inch) of brake pressure, and there is minimal pressure in the intake manifold indicating the engine is at or near full throttle, the ignition shuts off.

The system is designed to hold the ignition system in the inoperable mode until the system is manually reset. There is an additional switch added in parallel to the brake line pressure switch so the system's operation is insured in the event of a complete brake failure.
And short track/road race guys (like me) have used a simpler version for 20 years - an adjustable pressure switch, plumbed into the brakes, and adjusted to a pressure slightly higher than wheel lockup, which cuts current to the ignition.

And we have a real, quickly reached ignition switch, like this:

All you have to do is swat the red cover, it will shut the switch off!