You can "Hear Your Muscles." Do I really need to explain why this is a cool video? Okay, I will.
Because it addresses our goal with the “Try This Experiment Right Now” series-- which is to teach you how to do an experiment that teaches meaningful physics with no equipment other than what you already have in your pocket. Therefore anybody can do it.
The demos are unique, because most teachers don’t already know about this experiment, so it improves instruction in easy, timely yet awesome ways.