And on that note, I should finish my analog triple pedal build, and throw that in the mix as well! All three pedals are analog (though pretty short stroke, as piano pedals are), so that could be interesting.
I have a punch of piano VIs that support half-pedaling, and I think some have sostenuto logic as well, which would be interesting to try some time… (Only ever played real pianos where the middle pedal is just a half-blow pedal with a latch feature.)
As for the mouse, that just crossed my mind the other day, actually, but the problem is that it’s relative positioning only, which drastically limits its usefulness in this context. I think a tablet or pen screen (as I suggested earlier) would be much more useful here - another thing I should give a go one of these days.
That said, I suppose you could look at deltas from the mouse instead (well, that’s what they actually deal with on the hardware level anyway), and apply a leaky integrator to that. That would pretty much work as a 2D accelerometer. Not sure if it would provide any advantages over an actual accelerometer, though.