Mykle Hansen has posted a full tutorial on how to build his speed displaying vest for cycling. He’s using EL wire as the display, with an Arduino taking its speed from a wheel sensor. He’s hoping that this kind of speed display on his back will help vehicle drivers accept his presence. There’s a preconceived notion that cyclists are going slow, where you can plainly see, he’s keeping up pretty well. The only thing I would possibly change about this project is to move the display a bit lower on the back. When he’s really pushing the bike, he tends to lean forward making the label difficult to read. Maybe he should just put that below the numbers.