By using sensors and the Arduino interface board (15-20€), we created individually a sound device consisting of different sensors responding to touch and gesture. In fact we made a flat variable resistor made with some wood, plastic, tape and coppertape, connected it to the arduino board wich transformed the analog signals into digital ones which where communicated to PureData or Max/Msp via a USB-cable.
Wiz'n wise Wendy Van Wynsberghe explains how to make the resistor here