I’m not entirely sure how useful or practical this would be in a real world sense, but it’s still a pretty cool thing to have. Basically, it’s a vest that you wear while out riding your bike and it will show your speed to all the cars (and other folks on the road) on your back.
The Speed Vest project comes by way of inventor Mykle Hansen. The wearable vest contains a series of sewn-in numerals made from electroluminescent (EL) wire and they automatically show your current speed based on an off-the-shelf bike speedometer sensor. There’s an Arduino microcontroller involved too.
It’s a pretty nifty creation, but all that criss-crossing EL wire looks pretty ugly when not illuminated. Wouldn’t it be better to do a more conventional seven segment digital display, not unlike what you see on typical digital watches and alarm clocks? Yeah, you get boxier numbers, but then you don’t get all that extra EL wire everywhere. Check out the MAKE page if you want to make your own.