My P5 does not have a sunroof, and because of the lack of map lights between the viosors; I always thought that would be a good place for a pair or set of three gauges...But the roof liner is so flexible, it would be hard to get something mounted securely without going tapping through the roof...If anyone ever removed the roof liner, and knows whats under there...fill me in, I never checked...
That probably wouldn't be the best place to be monitering vitals anyway though...
As far as the pyrometer...I ony have a guess...I saw a few different types of meters remotely named that, but never for cars...Some guys refer to "reaction meters", in a exothermic reaction involving flames, as exactly that...And they display an output in terms of "joules", which is just a unit of energy...Some crazy guys could be attempting to get a read out of internal expansion energy, maybe in Joules, or in pressure...before anything is lost to the wheels...Possibly could be a way of trying to determine your exact engine hp before drivetrain losses (wouldn't be a Bhp number exactly, but an idea of how much energy your engine is creating)...I don't know...just a guess...and I have no clue how you would mount a sensor that could read that...