Espruino-based Guitar Pedal

Wow, looks good! Let us know how you get on with it...

One thing that might be pretty cool: Espruino can play back waveforms (including repeating them). You could use that for things such as tremolo, where you could choose the shape of the tremolo waveform.

You could also use it as a simple low-fi 'repeat box' - so it'd record while a button was pressed and would then loop it back. I have some code that I'd written for that that I can post up, but the lack of memory means you can't get a very high sample rate out of it if you want to repeat more than a second or two.