If you want to mod something – best choice is using LEDs. Rotating LED POV displays are one of cool ways to use them. Ch00ftech had some experience with building POV displays, so he decided to do something nice to his longboard. Longboard has 72mm diameter wheels so electronics need to be tight enough to fit in. Attiny24 microcontroller seemed to be just enough for this task. 14 pins obviously isn’t enough, so this is done using multiplexing.
Image synchronization is done using IR LED sensor with fixed reflector, which orientation can be altered to rotate image. In order to make PCB balanced he placed a coin cell battery to the center of PCB, so it would have no effect on ride. PCB design was another concern, because there are many types of longboard wheels. The idea of selling these started looking not so much attractive. But on his wheels it works perfect.