This is USB foot controller that has been reprogrammed and repurposed a few times. In it’s first life, it was an Arduino powered USB midi controller. I wanted the Arduino for my Theremin project so, later I switched it to a Teensy LC powered midi controller. I used it quite a bit to control plugins in my DAW (Studio One) while playing music. Then later I reprogrammed it again to be a USB mouse clicker. This was especially nice to have while fishing in Terraria. I could play my guitar and do other stuff with my hands while I fished in the game with my feet. Good times. I find it useful for other things sometimes too when I want to free up my hands. Like clicking through presets in a plugin in my DAW.