I have been looking into gauges and came across this: -
It only appears to be available for the Mk4 Golf and Mk1 TT, here some details from Awesome's website: -
The following are all data sources that can be shown on the gauge simply by flipping through the gauge menu:
Engine power / Torque / Boost pressure / Cmd pressure / Mass Air Flow / Air Fuel Ratio / Air intake temp / Exhaust temp / Coolant temp / N75 position / Dyno plot / Timing Correction plot / G-Force Display / 0-60mph acceleration timing / 0-100mph acceleration timing / Display and Erase Fault Codes
Not bad for £170 + the mounting pod
Only down side is I can't find any details on a version for the Mk5 yet