I thought the same thing, but was just tossing out what I read since I didn't build it. There will definitely be a movie made about this!The device already has a power source capable of detonating a cap (High explosive cant be detonated by heat, needs a primary) so they put a good size charge in the pager with room to spare. The heating up a battery thing is silly. There is no way they would have all went off at the exact same time from a uncertain battery heating technique. This was explosive.