I like my description better - sonic claymore.

 

I used the 1/8” jack with contacts on a joke device. It was a utility box, with several LEDs and a few switches, both toggle and slide. They were all dummies, not wired to anything.

There was one micro switch on the bottom. When the box was lifted, it latched a piezo buzzer on.

I left it on the corner of my desk. Inevitably when someone came into my office, they’d, out of curiosity, pick up the box.

The piezo would scream. No matter what they did with the switches, it wouldn’t shut off.

Until I bent a paper clip snd inserted it into the jack. I’d resurrect the device occasionally, when we hired someone new. Hilarity ensued!