You've basically reinvented the ultrasonic remote control: https://en.wikipedia.org/wiki/Remote_control#Television_remote_controls https://en.wikipedia.org/wik

You've basically reinvented the ultrasonic remote control: https://en.wikipedia.org/wiki/Remote_control#Television_remote_controls https://en.wikipedia.org/wiki/Remote_control#Television_remo... My grandma's TV had one of these - you'd press a button and it would basically mechanically impact a tuning fork to make the needed frequency.