Someone on the Vanagon.com list asked whether a temperature sensor in
the engine compartment would be a good idea. I think so...

Install a thermal sensor in the engine bay, somewhere near the top
andf off to one side (out of the way of direct flames... don't want
it to be killed immediately by a fire!). To it wire a fuel-shutoff
valve at the tank end of the fuel line. Rig it to kill the fuelpump.
Rig a siren and strobing superbright LED in the dash... LED aligned
to hit the driver in the eye.

  If the sensor detects excessive heat it will sound the alarm, flash
the LED and shut the fuel flow off at the tank and pump (no harm in
redundancy). It could also be set-up to activate a built-in
extinguisher system.