I really like Garmin for this. Lots of models to choose from to find your niche (eg, they have running focused, scuba diving focused, or just looks like a regular watch with no gps). What's cool is their ecosystem is NOT to do much smartwatch stuff. It's all about health focus. Or maybe fitness focus I guess.
Edit: oh I reread and saw you want blood pressure. They don't do this that I know of.