TireFly lights are button battery powered tire valve cap lights that blink when the wheel turns, but turn off after a few minutes when motion stops. Red ones are the favorites of the kids on my block. You can see them pretty well as they cross the street in front of you.
I tried two different set of these on my HD a few years back and they just kept flying apart going down the road. Maybe that is why they are called tire FLY. The ones I tried had the plastic end caps on them and were a real waste of money. Maybe some of the newer style would work.
I have them on my FJR, and notice them not at all... I'm not sure if that means they don't work very well or if I just don't look at my tires when I'm riding...
I was able to do a ride-a-long with my former college roomate in Detroit, Mich. Yeah, he's a cop. We pulled over many people that night including some "punk" who had those light up thingies on his wheels. don't draw more attention to the feejer, the shockwave is enough