I want a belt mounted or helmet mounted device with some big speakers on it that “notices” my gestures, and plays a prearranged recorded sound when I perform the gesture.

It couldn’t be that hard to do – put RFID chips on each of your fingers and and key spots on your arms, and you too can be throwing fireballs at people Street Fighter style. You could program the device to recognize your gestures, and it would determine what gesture you were performing by the RFID chips’ proximity and arrangement compared to the device.

Despite the fact that you might be able to offend people much more effectively, the idea has practical purposes as well. Traffic cops could lead the blind across the street with specific audible signals. You could teach a dog more effectively with consistent audible commands coupled with visual cues. Maybe the guys who call tennis matches might like it. Badminton? Football.