Probably it sounds too ambitious for car computer. It would be pretty hard to replace it. So this one only adds some features for your car including speed, RPM, instant fuel consumption and even more. It is called OBDuino as it is based on Arduino and it takes information form real car computer via OBD (On Board Diagnostic).
OBDuino can use various interfaces to connect to source like CAN. Each of them would require different interfacing chips. Arduino displays information on standard 2x16LCD which is also equipped with three push buttons for navigation and settings. So if your car panel isn’t showing you something, build it – it’s fun.