Hackaday writer of yore [Will O'Brien] has been working on this hardware for his motorcycle. Speed, voltage, gear, and temperature data is displayed on a 16×2 character LCD. The speed is pulled from the bike itself and the gear is calculated by comparing engine RPM to wheel RPM. He’s using the popular DS1820 1-wire temp sensor along with an Arduino to pull everything together. At this point he estimates there’s about $50 worth of parts, but that can be reduced by etching a board and just using the necessary components.