I just briefly glanced through the news looking into Omron products. I believe they are still waiting on FDA approval. That's quite interesting and could be very helpful for lot of patients.
Being a medical graduate, I have two problems with it. One, typical device has to be at the same level as the heart. I believe these watches would require measurement process where people would put their watches closer to heart or at the heart level. This means it cannot work passively. Second, proper measurement would require arteries running through it. There are two main ones around wrist while one around arm itself, but I believe brachial artery in the arm is relatively well exposed under pressure. Overall, it will be all about accuracy.
So yeah, I will correct myself. Not that, it can't be done. It will be quite interesting. It can make people more self-aware - help them control their blood pressure well and record logs for physician's review. At the same time, little natural peaks in blood pressure may cause anxiety - probably can become more of nuisance lol.