The Electrocuting Practice Robot is a fun idea machine created by YouTuber Ethan David. This robot has a terrifying function that makes an electric shock by moving the arm attached to the tip of the stun gun if it makes a wrong sound by discriminating the sound waves. Inside, there is an Arduino microcontroller, and the arm has a servo motor that reacts to wrong sounds and moves.
This product can be used to practice musical instruments such as playing a guitar, but it can be used not only for guitars, but also for other instruments. Related information can be found here.