Onno -
It was I who mentioned the voice commands. Glove-PIE is the program that I'm using. I've been using it for only a couple of days, but it works pretty well so far. I posted my version of the script in the iRacing downloads section here. Training windows 7 for my voice took about half an hour. One thing I did learn is that you have to turn Windows built in speech recognition off before you run the game, otherwise Windows will try to interpret everything you say as a command - which is fine if you say "press F1" but not so good if you say "oh cr*p" and it thinks you said "alt-tab".
Using the script in Glove-PIE allows it to interpret only defined commands and requires a button press for it to 'listen'. So if I say "Show Fuel", it presses F4 for me. I can then say "no fuel" to zero it out, "Splash of Fuel" zeroes it and adds 1 increment, "Full Tank" will fill it etc. Same with tires - "Show Tires" followed by "left sides" will un-check the right side tires. You could also do them one at a time by saying say "uncheck" followed by "down" to move to the next tire or "right" (or "increase") to add pressure. "Show Relative" returns the F3 display.
One thing I did not do was put the printed list of commands with the script, I'll fix that this evening.
If you have a non-English version of Windows, you may have some issues - at least that's what I gather from the iRacing forum thread - you'll want to read up there if you you do. There is an additional Microsoft module that may need installed if you are running XP.
I may end up tweaking the script further. I'll probably remove anything I have already assigned buttons to (weight jacker adjustments) and leave only the pit-stop, admin and chat related commands. (full disclosure: I still haven't tested the admin commands, nor the wedge adjustments for ovals).