Here is a cool video of a specialized form of light painting using 3-D models, iPads, and long exposures. It is from Dentsu London, a fun place to work from what I can tell. They released the iPad/iPhone app named Penki so you can make these videos too (if you have massive time on your hands). Here is a review of Penki.
iPad Light Painting
About the Author: Jeff Butterworth
Jeff Butterworth is the founder of Alien Skin Software. He used to create the products, but now he does marketing and gets coffee for the programmers.