it is possible to build an expressive pedal using the 3-axis MMA7361 accelerometer (you can buy this on ebay for 3$ CAD). we are dealing with a limited angle (1110mv to 1300mv) so the output of the x-axis needs to be subtracted and amplified: differential amplifier & op-amp voltage and gain calculator. the next step is to convert the analog signal to digital (using the ADC from your microcontroller) and finally interpret that in pure data (in my case). there’s a hardware low-pass filter but i am also using infinite impulse response low-pass filter in puredata (iir). feel free to write me directly if you need help reproducing this setup.
4 years ago i built an expressive pedal using a led and a photo-resistor:
there is also this solution using capacitance sensor and v-usb:
of course, the traditional potentiometer solution: