Side project idea: ultrasonic jammer. It's really simple, just use a piezo speaker and drive it with a small microcontroller (or an analog circuit) to jam the f

Side project idea: ultrasonic jammer. It's really simple, just use a piezo speaker and drive it with a small microcontroller (or an analog circuit) to jam the frequencies they're using. The only problem is that dogs and other animals won't like it ;)