I just bought this thing called a ScanGuage. It is like a 4"x2"x2" electronic box that is a code reader and displays 4 guages at one time in real time while driving. It only has one plug and that is the OBD 2 port. But best of all is it will do speedo corrections for gears/tires on as many vehicles as you want. It doesn't marry itself.
Here is a list of the guages available on it:
-Fuel system loop status (closed or open)
-Intake air temp
-Water temp
-Gallons of fuel per hour
-Ignition timing
-% Engine load
-Miles per gallon
-Miles per hour
-RPM
-Throttle position
-Battery voltage
-Gallons per day
-miles per day
-gallons per trip
-miles per trip
-Distance to empty
And best of all it is only $124.95
Link: ScanGuage
Here is a list of the guages available on it:
-Fuel system loop status (closed or open)
-Intake air temp
-Water temp
-Gallons of fuel per hour
-Ignition timing
-% Engine load
-Miles per gallon
-Miles per hour
-RPM
-Throttle position
-Battery voltage
-Gallons per day
-miles per day
-gallons per trip
-miles per trip
-Distance to empty
And best of all it is only $124.95
Link: ScanGuage