Several years ago, Consumer Reports did a test of the pen type tire gauges. They included a couple of early digital models and a dial type or two also. As they always do, they bought dozens of the same brand, model, etc, from different locations around the country. End result is that they tested probably hundreds of gauges and found that all of the pen type were within 1 lb of each other and being accurate.
CR actually had trouble picking the "best buy" or top rated one, because they were all so good. They ended up picking a couple based on the angle of the head and how they felt in the hand when you were pushing them on a tire valve stem.
The digital gauges and the dial type they tested were way off. Times have changed, there are digital gauges that are accurate, but I suspect many are not.
Many years ago now, the airline I work for bought Schrader digital gauges that they made special for us. They were just like the 150 max auto gauges that Schrader made, but were capable of 300 lbs instead. These gauges were tested every 6 months by the company calibration room and found OK, but the ultimate test (so I thought) was when we did a cockpit print out of the tire pressures and then took the Schrader gauge and checked each wheel and compared it with the airplane's electronic tire pressure read outs. They were always within 1 lb even though we were dealing with 200 lbs or so of tire pressure! The company did away with the digital gauges however, as they found the mechanics were wasting alot of time being **** and trying the get the pressure exactly right, when a couple of pounds just really didn't matter. We went back to dial type gauges that you can only read to about 5 psi.
Edit: looking at the Schrader web site (confusing and circular) I found that while they manufacture electronic TPMS components, test equipment, etc, they do not see fit to manufacture or sell a simple tire gauge. (there are some dial gauges in the Schrader France catalog)
That being said, tire pressure on an auto or truck is especially important in these days of high gas prices (and Explorers running tires too low).
Get a couple of good stick gauges and depend on them.
Charles
