I always thought that the kinetic powered bike lights were a cool design; then I saw this. Although only a theory, the design should work. This concept uses the motion of the bike tire to spin a felt wheel that drops a trail of colored chalk from a hopper. The end result is a colorful trail that shows other riders and drivers where bicyclists have traveled. A nice way to leave your mark, a great way to find your way back, and a perfect way to promote safe riding practices. But, again, it is only in the concept stage, so we will have to wait!