Kill switch extension cord.

[mklotz]

Yep. I was thinking the same, that in actual emergency, this kind of button doesn't always work, you need to hit it.
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One that works when you kick it or something like that, without need to hit the actual button ( its somewhat small target )
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Perhaps a mercury switch in an appropriately shaped box. Knock the box over and the switch turns circuit off. Another possibility is a plumb bob in a ring. When the container is jostled the bob hits the ring and completes the circuit that disables the power.