Non-intrusive technology which can work at home to monitor people' vitals is a game changer, there are so many applications to this. Research is at the beginning.
Indeed there are privacy issues with big providers doing this, but then this really opens up so many possibilities if done well.
Also, I believe that if Apple is working on blood glucose estimation, it's probably not the way described in this article.
I could be wrong that Apple will do it this way, but the current hardware supports different wavelengths PPG, (as well as the Samsung Watch Galaxy 8), which might be able to use to estimate blood glucose variations. But it's pretty complex, especially to generalize.
I wouldn't be surprised if they start like blood pressure, just estimations as to how it's going up and down.
I know that because I'm literally working on this with https://trackourhearts.com, using an AI model I created to estimate blood glucose, though I'm doing it in a personalized way so I can provide more absolute estimates but it's still incredibly hard from PPG as the wavelengths available aren't the most optimized for this.