Reactive Glowsticks was a project I did over the summer of 2009. I saw many glowsticks available had LEDs in them, and some even flashed colors and patterns to create interesting persistance of vision effects.
When I noticed that accelerometers had recently fallen from their previous price of $15 each to only $4 each, I searched for projects that took advantage of this to make glowsticks that changed color depending on their speed or other aspects of their motion, but found none.
Thus the Reactive Glowsticks project was born. I built 5 prototype glowsticks, each with 8 LEDs and a tiny microcontroller and accelerometer, along with highly efficient power supplies. Each glowstick is emits a pleasant glow ranging from green to yellow to orange to red depending on its speed. They're powered by a single AA battery that lasts around 6 hours.
After I finished building the hardware, I invited some friends who spun glow poi to a photoshoot to capture long exposure shots of them spinning with my Reactive Glowsticks. You can see the results on this page. The spinners quickly acclimated to the glowsticks and were soon able to control the colors and patterns they produced.