The RB199 in the Tornado was one of the first to use optical pyrometers to record and control EGT. They were more accurate than conventional downstream thermocouples but they were much higher maintenance because of the tendency to soot up. They were supposed to be cleaned every 25 hrs, calibrated every 50 hours and performance tested every 100 hrs. The 25 hr cleans were frequently "cuffed off" but you can see why such a regime would be prohibitive for civilian applications. I've not really kept up with the civilian engine sector over the past 15 years and I'd be interested to know if any modern civvy turbofan uses pyrometers.