You could use a scheme kind of like how port-knocking works. For example, plugging in directly causes self-destruct, but plug and unplugging twice in 5 seconds will be the "okay it's me" signal.

This could be implemented by writing a timestamp file on wakeup.

> This could be implemented by writing a timestamp file on wakeup.

You’d need to embed a clock and an energy source to keep the clock going.

A 150uF capacitor should keep the microcontroller running for about 5 seconds without power; it could keep time. 7.3mm x 4.3mm x 2.9mm