Back when this became an important realization at GasSavers, I sprung for a decent, racing-grade guage.
The gauge housing has a rubber surround to protect it from getting battered, and it holds the pressure until you press a button to release the air it's stored. I once had a digital keychain guage, but it was fairly unreliable and gives the "digital effect" -- e.g. digital speedometers. Sometimes a number needs a visual reference around it (analog).
It's spot-on -- and if you're fiddling with lining-up the guage inlet in cold weather, the design lets you get the maximum value stored to compare with the next tire once you get it on there properly.
I found it at the Auto-Parts store for about $25. Now all I need is that "laser" (Dr. Evil reference) that gives you temperatures of it's target.
Rh77
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