tells everyone how fast you’re going

meh - only “Up to 70 miles or kilometers per hour”

Good idea.

Cool concept, but in practice, would any driver take notice?
Hey look bro, that dickhead on the bike has got illuminated numbers on his back!

it would be fun to ride between the cars while they’re gridlocked, at 25 kph.
or, overtaking super commuters, or people riding on beach rd.

I would just try and ride as fast as I could everywhere so people thought I was hardcore. I would be worried about embarrassing myself. At least with my little computer I am the only one that can see how slow I am.

It should throw up the odd subliminal insult (and middle finger image) as well.