I use Accutire Digital gauges. I have 3 and all three are accurate to +/- 0.5 psi when I test against ISO Lab-certified master gauge at 80.0 psi.
They run about $15 on Amazon.
I have done gauge checks at a couple of FMCA Conventions and find that pencil gauges, as a group, are the worst because they get dirty and the "slip stick" in many have nicks in them from rolling around in a toolbox. 14% "failed" and were off by more than 5 psi.
Analog (dial) gauges are sometimes difficult to read as the dials may only have marks every 2 to 3 psi or so. Their failure rate was about 5%.
Concerning TPMS accuracy
I tested 6 TireTraker external sensors and 6 TST internal sensors and found them to be within +/- 2.0 psi against the Accutire master gauges. I have published the data on my RV Tire Safety blog.
At my RV tire seminars, I have suggested the following system for checking and managing gauges.
1. Get a couple of Digital gauges and compare them to each other. If more than 2 psi difference at 80.0 psi then one or both are questionable. When you have two digitals that read identical psi (+/- 1.0 psi or less difference at 80.0)
2. If you have dual rear tires and need an angle head or "dual foot" like this
to read the outer dual you can still use that stick or dial gauge on your duals and then confirm the reading of a front tire against your "Master" digital gauge to confirm the "stick" gauge is reading correctly
3. Keep one digital as your personal master but do not use it for your daily or monthly check against your TPMS.
4. If your daily "dual foot" stick gauge or dial gauge gives strange readings compare it against your personal "Master" digital gauge that you keep packed away in a padded box. It is very unlikely that both your "master" and your daily gauge will go "off" the same amount and in the same direction (higher or lower) at the same time.
Using the above system I have been able to confirm my digitals are ALWAYS accurate to +/- 1.0 psi or less difference over the last 12 years except when the battery "died" in one digital. After replacing the battery that gauge was confirmed to match the master again.