If I'm not mistaken, the first Zenith TV remote controls worked by plucking a tuning fork, which the TV presumably detected using a microphone and a bandpass filter.The great advantage being that the remote needed no batteries.
Now, with the onset of warm weather I have set up some our fans, one of which comes with a three button remote control. I hate digging up and buying batteries for remotes.
So, I was wondering if it would be possible to convert the remote into a tuning fork actuating remote, using something like a PLL to detect which button was pressed Where could I get such tuning forks? Or could I sacrifice a harmonica to get reeds that vibrate when plucked?