i just did a quick port of max & michael egger's fingerpinger to PD. this allows apple trackpads (under os x) to be used for multifinger control. source and external are here. if you want to improve this, you will need to compile with the MultitouchSupport framework.
http://soundhack.henthorne.org/soft/fingerpinger_pd.zip
tom
tom erbe ~ tre@ucsd.edu ~ studio director - computer music ~ ucsd department of music