I think it would be super easy to convert one of those auto glow light packs to a brake light. They have some kind of battery in the pack. Change the battery pack to rechargables, rig up a simple circuit and - bam! - brake lights!
yea these LED's are crazy bright, they about blinded me when i put them in front of my face to see how bright they were. now i constantly have the feeling that there are car headlights behind me lol