A spoke on a bike wheel is something that can move fast and this is why the Spoke POV has been created. You attach an LED device to the spokes on your bike and program it to display text on your wheel. As the wheel spins you can see the text floating in the air. The project includes a free schematic design, open software for uploading and editing stored bitmap images, and a high-quality kit with all the parts necessary to build your own. They are 30 LEDs on each side (22 for BMX) x 256 radial pixels, runs on 2-3 AA batteries for 10 hours. It’s kind of a cool little toy to have.
You can check out more details over at SpokePOV: LED Bike Wheel Images.