makerfaire.com:

Maker Faire Bay Area 2009
The Speed Vest

Location: Expo Hall 132

The Speed Vest is a bicycle safety device and advocacy tool that displays the wearer’s current speed on their back in easy-to-read lighted numerals. It improves rider visibility and legitimizes bicycles on the roadway as a fun and efficient way to get around.

Web site: http://mykle.com/msl/?p=10

About the Maker(s)

Mykle Hansen & Brady Clark [
Mykle and Brady have been dreaming up and realizing hare-brained schemes since their collective noggins sprouted their first hairs. Normally gravitating towards the sublime and the absurd, this project marks their first collaboration. They both ride bicycles for fun and transportation and advocate for better biking in their local communities.
http://mykle.com/msl/?p=10