My advice would be to buy a cheap stethoscope and BP cuff. Then you can teach a wife/girlfriend/family member to take manual readings.
Slightly less convenient that a digital cuff, but at least you can trust the results.
The only time I ever use our expensive monitors is in the interest of time. As soon as time allows, I'll check a manual BP for accuracy.
Great idea, but where can you take a class, though, for that? Do the First Aid certification places teach taht in other classes or what?
You don't need much of a class to learn how to use one. It might look super scientific, but it's far from it.
I'd imagine that there are plenty of YouTube videos that can walk you through it. Once you get the basics down, a little bit of practice and you'll be all set.
Trust me, it's a very simple process and can be learned within a few minutes. When I teach students to take a manual BP, they usually pick it up within a few attempts.
I could spell out the steps here, but it's probably easier with a visual aide like YouTube.