OS X users intrigued by the possibility of controlling sound with a Wacom graphics tablet, here are more resources for you, helpfully offered by a guest comment:
- Music Unfolding's µMIDI Controller,
US$15 shareware (which also works with your mouse, if you prefer) works
with the Wacom tablet, though looks like it hasn't been updated since
2002. - Max/MSP Wacom support external for OS X, free
- SuperCollider audio synthesis language for OS 9/X, free; includes Wacom support
Let me know how it goes, if you've got a Wacom handy! (I'll worry about getting one for myself cheap.)