I found a nifty little valve from grainger that is a catastrophic leak stopper. If flow in the line exceeds the rating, it pushes a ball into a seat against a light spring pressure to seal the line. No flow in a pressure gauge line to speak of unless it pops a leak.

The other reason I like mech pressure gauges is that they are easier to read fast, and the needle movement is an eyecatcher for me that a changing number is not, and I don't think the moving perimeter leds would do it either. Just personal pref.

It's easier and much faster for me to spot a gauge with a needle out of place than it is to read and compare a number.