A selection of electrical components from Britpart ? That'll keep you guessing too !
Seriously, after your recent experience I can see why you are keen to improve security.
Simple stuff like a battery isolation switch, hidden away out of sight ? The old favourite of a blinking red light ?
Leave the transfer box in neutral.
Bolt-on stuff like a clamp plate over the pedals ? Saw one in the mags that folds flat on the floor when not in use.