Homemade Heads Up Display For Bicycling?

An anonymous reader asks: "I am a geek that bicycles in an urban center. After seeing this commercial product, I was interested in the possibility of building a homebrew HUD for a bicycle helmet. I searched the usual places and couldn't find much so I thought I'd ask the readers of Slashdot. A HUD that displays speed, distance, and cadence seems very feasible as many bike computers collect that data. A great longshot would be a range-finder that told you the distance to the object you were turned toward, but I'm not crossing my fingers for that. So what components would be needed to make such a cool device?"