Brainwave that made elevators safe

Elevators (lifts) are complex devices. But the fundamental safety device is incredibly simple. Electromagnetic brakes are held open while there is electric current. In the event of an electricity failure, the brakes are released and the elevator comes to a stop. What a great idea. Simple, positive. I love the thought that the absence of electricity triggers the safety mechanism. Its the inverse of what one might expect. Elisha Otis patented it and created the "safety elevator". How might thinking about the inverse of something create a new product or business opportunity today?