This isn't too far from using a logic probe to test hardware circuit. It has a tone for LOW and a tone for HIGH, and you can listen to what state pins are in, e

This isn't too far from using a logic probe to test hardware circuit. It has a tone for LOW and a tone for HIGH, and you can listen to what state pins are in, even if they're switching faster than your eyes can see the LED flicker, you can hear the pitch changes.