have a look at adjustable thermal breakers from the sparkies end of the world.

they work like a self resetting circuit breaker but use a trip contact which you can adjust the preload on to set the desired trip point.

its also worth putting a LED across the connections so that if the breaker goes you get an indicator on the dash an alternative if its still available would be one of the breakers that once it open its primary contacts it also closes another electrically isolated set which are usually used to operate and alarm circuit on an independand supply.