I didn't reverse-engineer the protocol for my blood pressure monitor in 24 hours

I am having issues with hypertension and purchased one of these:

https://hilo.com

You put on a cuff (supplied) to calibrate it, and then you wear a little gadget on your wrist. It takes frequent measurements throughout the day and night when it senses you aren't moving. It then syncs with your phone to store the results. Its a little pricey, but seems to work well[1]. And it avoids the faff of a pressure cuff[2] and 'white coat hypertension'.

[1] Apart from the option on the app to do a reading from your finger using your phone camera - which gives wildly different results to a cuff.

[2] You need to recalibrate it every month or so using the cuff.

how accurate is this?

It seems pretty consistent with a cuff. Also it doesn't jump around wildly from one minute to the next.

> The Hilo Band uses photoplethysmography (PPG)—an optical sensor technology that collects data from your wrist. This data is sent securely through the Hilo App to Hilo’s cloud server, where advanced algorithms estimate your blood pressure using Pulse Wave Analysis (PWA), which looks beyond just the rate of your pulse, and examines the unique form of each heartbeat’s pressure through your blood vessels.

I doubt that it’s comparable to real blood pressure monitor.