Overhand knot in a strip of carbon-loaded paper becomes an FSR that can be easily connected to your favorite microcontroller (in this case a teensy running with the Arduino C++ tool chain).
This is part of my Fingerphone [1] instrument.
Links:
[1] http://adrianfreed.com/content/paper-fingerphone-case-study-musical-instrument-redesign-sustainability
[2] http://www.adrianfreed.com/category/affinity-group/analog-electronics
[3] http://www.adrianfreed.com/taxonomy/term/173
[4] http://www.adrianfreed.com/category/affinity-group/maxmsp
[5] http://www.adrianfreed.com/category/affinity-group/surface-interaction