I completed a simple prototype of the speedometer/odometer circuit on a breadboard. Prototype PCBs are in production now, from SeeedStuido. The PCBs came to ~$35 for 10 boards, and the components are almost $100 / board. Most of that cost is LED displays, and the MAX7221 ICs.
I haven't written any code yet, except to test that I am able to drive the stepper motor and display drivers, via arduino libraries. Since this project is primarily about learning, I plan to write the firmware from scratch with the AVR-GCC toolchain.Of course I'll post everything on github when I have a chance. For now if you're interested in contributing contact me directly.