I remember many years ago receiving an Intellitouch clip-on tuner for Christmas, and thinking it was basically witchcraft. How did it know what note was being played? There was no plug, no microphone, just black magic. At the time, it was the only one of its kind, and they were something like $70.
Now you get clip-on tuners free with your order of this and that, in gift bags as advertisement, and I’ve got like 5 I don’t need. The technology turned out to be pretty simple and cheap to make, not witchcraft at all (witchcraft is cost prohibitive anyway) so several companies were able to reverse-engineer the idea and saturate the market.
Now TC Electronic, makers of the PolyTune polyphonic tuner pedal (the one where you can strum all the strings at once and see which is out of tune) have announced the PolyTune CLIP – a clip-on version.