A quick and dirty experiment (3 hours dev time, excl. previous work) using Processing and JTablet to use my old Wacom tablet. I wanted to dust off my tablet and figured returning to my fireflies sketch would be the quickest way to test the library.
The fireflies are drawn when pressure is applied, with their size corresponding to the pen pressure at the time. I also added a method to return them to their start location when a key was pressed, simply so it was possible to draw (often rude) shapes with them.
The word 'Processing' should be visible toward the end of the video. Having spent a few hours after a long day adding this stuff I ended up tiredly rushing the final 'recording' and, randomly, added a music backdrop, mostly because I just figured out how to do so. It's also rather short. The music is by Squarepusher and is called 'Tommib'.
Tablet library: http://www.cellosoft.com/sketchstudio/