My old friend had a book titled something along the lines of, "Gadgets for Mad Geniuses." It showed how to build all of these devices from Sci-Fi books, things you could use to take over the world, and it showed their construction in very practical terms. One of them was an Electro-Magnetic Pulse, an EMP. It's basically a gun you blast at something to fry all of the electronic circuits killing it instantly, or that's how I understood it. We brainstormed what we'd do if we created it. We couldn't blast cars driving past because they'd just coast to the end of our street. But it might come in handy at a bar when a bartender is about to run your credit card to pay for a large tab. We decided not to build it, because it turns out they're very illegal. Also, it could have been a disaster if someone in the bar had a pacemaker.