well if i understand right an idiot key is one that works on the doors but not the ignition that you can (for example) hide in a magnetic box attached somewhere on the underside of the car so you can get back in if you leave the ignition key in the ignition and lock the door but nobody can steal your car with it
i've had two cars with powerlocks that won't lock if a key is in the ignition, and another SORT OF anti-locking-yourself-out mechanism is the doors you have to lift the handle on to close, because if you're distracted enough to leave keys in the ignition you're probably not gonna remember to lift the handle either
but i've locked keys in every damn car i've owned, so fat lot of good that does