@todbot We could have used one of these at one of my previous jobs... we had just acquired another company and we brought their engineers over to see our server room. In their office, you had to swipe a keycard to enter a door but you
had to press a button next to the door to exit it. So when they left our server room, one of their guys instinctively pressed the button by the door and KACHONK. Everything turns off

At a later job I told my boss this story and said we ought to put some sort of a guard on the emergency shutoff button. He said "Don't worry, it's not connected to anything"