This is a frustration that avid cyclist Mykle Hansen has dealt with countless times, and sick of cars honking and giving him grief, he decided to do something about it in the form of a vest, which not only increases his night time visibility, but also displays his speed on the back of his vest in 7” tall numbers.
It looks like a simple setup, requiring an off-the-shelf speedometer, which feeds data to an Arduino that is hidden away in the vest. The Arduino then lights up the electroluminescent wires sewn into the vest (as pictured above). If you’re an avid cyclist and this sounds like a great idea, head on down to Mykle Hansen’s page for the instructions.