Scan your friends to see if they're lying. Lie-Detector is a fun trick to play on your friends. You secretly control Lie-Detector to go off when you point it at your friends. It pings like a radar as you scan your friends and you choose when the alarm sounds indicating the presence of a lie. It always gets a laugh. The trick is so simple, but yet very difficult to detect how you make the scanner jump from low to high as you point it from friend to friend and ask them questions.