it works pretty well

the cable between the ardunio and the display, i just chopped an old usb cable.

i ended up going with a really tiny sparkfun ardunio clone, as the uno wouldn't really fit in a container i liked.

external circuitry was really minimal, just a cheap switching power supply, a few lm7805s to step down the signal and high beam inputs to 5v, and two diodes for the signals so i didnt have to add a third regulator.

indicator logic: uses the first digit for signal (S) and high beam (H) (alternating), second digit for neutral (n) or the hundreds of speed (100+kph you aren't going to be in neutral, hopefully) and the last two digits for speed only.

it does FI light and oil pressure too, displays 0IL or ECU alterating with the speed/indicator display when these errors occur

inside, it's really hacky and circuit boards are held together with silicone, but i think it'll live.

speedo seems really accurate up to insane speeds, calibrated with GPS