> Requires a third-party blood pressure cuff (sold separately) for initial and periodic calibrations

So you still need a wear a sphygmomanometer: https://en.wikipedia.org/wiki/Sphygmomanometer

I'd read that differently. periodic doesn't mean continually. I'd expect you'd need to calibrate against a sphygmomanometer weekly or something to that effect. Still a lot more doable than wearing a blood pressure cuff 24/7, even if the calibration interval is fairly frequent.