I have driven off with my parking brake partly engaged on a couple occasions and today I had a brain flash! I mounted a brake light switch that is normally closed on the parking brake bracket, I grounded one of the two lugs to the bracket and ran a wire from the other lug to the brake wire on the master cylinder. Now when the key is on and the parking brake is engaged the "brake" light in the dash lights up until I release the parking brake. It was a ten minute operation and works perfectly.
This is the switch with the brake off and the circuit open.
This is the switch with the brake engaged and the switch closed, activating the "Brake" light in the dash.
The Brake light on with parking brake on and key in run position. The light goes out when the key is off or in the acc position
I bent a thin piece of steel and drilled a hole for the switch and two mounting screws. You can see the ground wire conneted to the mounting screw.