I use Pentax spotmeters for everything, even if the camera I have along happens to contain its own TTL metering system. It's more accurate. And there are quite formal standards for calibrating these so that NONE of them differ. Hollywood filmmakers depend on that fact. So do I, especially given the cost and fuss involved shooting color sheet film. Incidentially, I keep one away in storage unused, both as a potential spare someday, but mainly as a reference to check the others from time to time. Mine are all Pentax digital spotmeters (prior to "digital" becoming a dirty word), and seem to need a minor recalibration or internal cleaning about once a decade apiece. That statistic is improving, since I won't be around long enough to need calibration service much again. I have zero experience with older models of Pentax meters, so am not contradicting any warnings with respect to their repeatability.
So yeah, it is analogous to thermometers. And that's why Certified thermometers exist, which are based on even more expensive thermometers. Heck, up the hill at the LBL national lab they have thermometers accurate with millionths of a degree (bigger budget than you and me too). A basic Kodak Type III Process thermometer is all I need, and it's equivalent in accuracy to other certified scientific bulb thermometers in the $250 to $350 range. But no, I'm not the type to order a cheap turkey roasting thermometer from Amazon and repurpose it for the darkroom, simply because turkeys were routinely overcooked or undercooked due to its inaccuracy!
As far as watches go, I never wear one.
