Now I have this blood pressure monitor device that doesn’t work without a logged in app and is a paperweight. I’m lucky I never invested into their ecosystem of health products. Lesson is no matter how popular a brand is, there is no guarantee they will be around. I’ve lost all my health data and there is no way to get it back.
One company that I can recommend is Withings. They do have an companion app, but a lot of devices do work on their own, and when not, they work with Google Fit or HomeAssistant, though probably due to that fact the products are pricier.