Think of them as advanced FitBits…

The Blood Pressure Monitor industry? Apparently.

https://search.brave.com/search?q=home+bp+monitor&source=web

Can home blood pressure monitors give false readings?

Yes, blood pressure monitors used at home can give false or inaccurate readings, oftentimes due to user error. Wrist blood pressure monitors tend to be less accurate in general than upper arm blood pressure monitors. If you want to measure your blood pressure at home, most experts recommend using an upper arm cuff and following the product instructions carefully.

The above search result was taken from a Frequently Asked Questions panel buried at the bottom of this page:

https://www.forbes.com/health/healthy-aging/best-blood-pressure-monitors/

Forbes HEALTH?

Pure sales page with the usual obligatory information and “facts”.
An in-house affiliate program.

There must be a huge market for these items. I wonder why?
No, I don’t actually wonder why.