Battery gauges, have dead batteries every time I reach for one... (not that often)... ...

I have found the mechanical ones with a square readout tube, to be more consistent than the kind with a flat tube...

... but,.. don't be overly concerned anyway.... air pressure is not that exact ... it changes minute by minute, as tires heat and cool, and barometric pressure and elevation changes...
...a few pounds either way, don't mean... diddly...
...

I have a guage in each car or truck and one in the camper plus one on my bike. I don't give over $5 for a guage and do like most with the square slide. As for accuracy, check them all on the same tire and see if they are close to each other. If not toss, it. I have a plug in 12v compressor with built in guage my wife bought on clearance for $5. It is about 3lbs optimistic, so I use it anyway and allow for the error.

Use what you like, but please understand a low tire will squirm out from under you in a curve.