I wrote clutch to let me use this $9 foot pedal to control vim without hardware modification.
http://www.amazon.com/gp/product/B0098PLPOI/ref=oh_details_o00_s00_i00?ie=UTF8&psc=1
By default the pedal just sends a "b key pressed" event when you push it down and a "b key released" when you lift your foot.
This very small utility lets you define what keys you actually want to happen when the pedal sends these events.
By default, it will emulate tapping the i key when you put your foot down and will emulate tapping the ESCAPE key when you lift your foot up.
Please read the very short one-file source to see what other keys are available.
clutch MUST be run as root. OSX only allows root programs to hijack USB keyboards ( the os thinks the foot pedal is a one-key keyboard... )
default: i on down, ESCAPE on up:
sudo ./clutch
Example: a on down, ESCAPE on up:
sudo ./clutch a
Example: a on down, ESCAPE on up, but ensure that SHIFT is held down while a is being pressed (has the effect of A in your editor)
sudo ./clutch a ESCAPE SHIFT
https://github.com/alevchuk/vim-clutch is the first implementation that I was aware of. Unfortunately, it requires hardware hacking. I just use the operating system's accessibility API to fake the key sends, so no hardware hacking needed for "organ playing".
I would really like to be able to program a series of keyboard events for each foot pedal event.
I am currently thinking of a mini dsl like this:
./clutch 'ESCAPE,+SHIFT,a,-SHIFT' 'ESCAPE'
This would let you specify arbitrary key events (using + for pressing and - for releasing, with neither for a simulated 'tap')