I actually wouldn't mind doing this to my W210. I know, it's popular with the neon and boom car crowd, but I don't car what fads they follow and they don't influence my decisions one way or the other. It would have to be off-white to match the rest of the upper part of the interior.

I'd like to put a voltmeter in there. Also handy would be a AC high-pressure gauge; I believe that I could tap into the signal coming from the dryer and scale it with a small electronic circuit. Exhaust temperature is another possibility, but without a turbocharger, it's much less of an issue (right?).

No chance of doing such a thing on our Jetta. In an accident, the airbag would launch it into your face.