As mentioned on this and many other websites, the ScanGuage or other iFCD (Instantaneous fuel consumption display) is vital to measuring the effectiveness of any green driving tip you might try. I use the scan gauge II pictured above. I admit the mounting of it is not ascetically pleasing but I like the fact that it is positioned where I can see it without taking my eyes off the road.
I hate to do anything drastic like take the dash apart but I am thinking about ideas to mount the ScanGuage in a better location so the wire is not hanging down. For the time being though this will have to do.