In general, do you think that most pharmacies regularly and properly calibrate their blood pressure arm monitors?

Not likely --: They are probably checked bi-annually (if that)--but a given BP cuff is usually intrinsically accurate--meaning that if you compare the readings you get only against it, then your range / fluctuations / etc., will be correct, even if the exact #s are a little high or low--this is why we tell you to use one machine to the best of your ability.