"I'd also like to make a plant into a theramin, any suggestions greatly appreciated. I saw the 'twittering plant' on the 40 arduino projects link above, that lets you know when it needs watering, but that's not really what I'm after. I want to make the plant into a musical instrument." - Helen
Have you seen the Drawdio? http://web.media.mit.edu/~silver/drawdio/ - nikki