I installed a gear indicator. I did not want to just tack it on someplace, so I installed it in the LED panel. I was going to try to remove just the Neutral LED and replace it with the gear indicator, but the indicator was a bit too big. So I replaced the whole panel. I got some LED indicators to replace the High Beam and Low Fuel indicators. I had also gotten Turn Signal indicators, but mounted them up on the speedometer for better visibility.
To make the new panel, I first fitted a cardboard form, then used it to cut out some sheet aluminum, which I bent up with a vice. I painted the front of the aluminum black and fitted a blue acrylic face. The blue acrylic makes the indicator easier to read, as it blocks all but blue light from reflecting off of the 7-segment display face.
There are at least three different types of these indicators. One type uses a magnet on the shift mechanism and a pair of sensors mounted nearby. Another uses the tach and speedo signals to "learn" the gear ratios. This one plugs into the diagnostic connector and gets its info from the ECU.