Back in 2002, I decided that I wanted to let the other drivers on the road know what I was getting for MPG.
I mounted a tiny color video camera on a bent piece of solid # 14 wire, which I stuck into the slot between the dash bezel and the steering column bezel. The camera was carefully focused so that only the bargraph and MPG displays were in the field of view. I made a waterproof rear LCD video display and fed the video signal to the monitor.
It was a bit too dark for full sunlight viewing, but was quite readable under most other conditions.
I hated it. I felt compelled to drive in my most efficient way, since everyone was watching, and finally took it out for that reason. Now if I were a hard core hypermiler that always got super numbers, it would have been another story.This was before MIMA, so maybe I need to dig it back out?