[zagrot]

why would you want to? though most people may not think so it takes a lot of time to see a number, recongnize that number, and apply that information in a usefull way, especially when you are doing other things -- like driving. for about a year i drove a crysler lebaron that was equiped with a digital numerical speedometer (think alarm clock display). i would often find myself staring at the speedo for several seconds before i realised whether i was speeding or not (more often when i was very tired), whereas with an analogue gauge it is possible to memorise relative needle positions and obtain the required information at a glance.

project difficulty, since you asked, is high if you cannot find a pre-produced gauge set with the features that you desire. by the way, the obdII computers have the capability to output a digital signal for nearly every sensor the car has and this information can be accessed with a specialised adapter and a personal computer with the appropriate software.