SMIP is an attempt to hook a footpedal up to my workstation, increasing the number of non-mouse input devices (thus decreasing the amount of mouse-usage).
SMIP is, essentially, a keyboard (musical) sustain pedal plugged into a keyboard (computer) controller. The pedal acts as a momentary switch, closing it generates a keystroke. Initially I tried tracing the matrix circuit to find a rarely used key combination (eg Super_R + SysRq). At some point I realised that the setup could be wired to generate unused keycodes (in this case, keycode 131).
With some xmodmap tricks, SMIP could probably be used as an additional modifier key, although at the moment a single keystroke is enough for me.
The driver. You'll want to replace the ``printf("Whee\n");'' with something useful. Requires X Windows.