After that long thread in hardware>suggestions about spectrasol, I started to wonder if we could just figure out how to make out own touch sensors. Seems like it is just conductive ink printed on mylar. A little research turns up something called "piezoresistive ink". Does anyone know of a supplier for this stuff or something similar? It seems like it might be possible to just print these in a modified inkjet printer.
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If you take a look at Interlink's Force Sensing Resistors you can get an idea of how they do it. The two conductors are interleaved like woven fingers, (but never connecting) on the bottom. Above it is a resistive material, the harder you press, the more of it connects with the conductors. If you mix that with some of the information on how to make your own ribbon controller with magnetic tape, you should be good to go.