Once at a trade show, someone was selling a motion detector defeating device. It was basically a small fan with slow moving blades. It was powered by plugging it into a USB port of a laptop or other device. One of my coworkers purchased one and reported that it did work. The only problem was that the USB power cable on it was not long enough to reach from her laptop to near enough the detector for it work without moving the laptop to an inconvenient location.