Comment by nwiswell
> Inside the battery is perhaps the best hidden, but you'd need to own a bunch of battery manufacturing facilities (expensive).
Do you?
What stops you from just taking a smaller battery and packing it with some plastic explosive into the typical "battery foil"? I'm sure the IDF is capable of doing that at scale.
Something along these lines is my guess. Focus on the batteries. You can replace individual cells with explosives and cause the remaining cells to overheat to start the explosion.
Most battery packs have integrated power management chips, so you could focus on modifying the battery firmware.
You could have another component send a message to the power management controller to trigger it.
You could also use the power controller's internal current sensor and clock to watch for a device event (power draw from the screen at a certain time or the power profile for a specific set of CPU instructions), giving you means to trigger it without modifying any other part of the device.