I've seen marching timpani with tuning gauges, but never in an orchestral setting. I've always wondered why...I loved playing them in HS. My band director wanted me to go out for All State but I was not confident enough even though I was singled out in competitions sometimes by the judges, which really surprised me.
I had to learn to tune by ear. I was amazed when we went to a competion once and saw that the timpani's being supplied had some sort of tuning gauge built in and all you had to do was move the pedal according to the pitch and it was relatively spot on.