I saw the DIAM Tech video, it is suggesting in their video that their buisiness model would likely be to lease even the personal device, for £100 (Euros/dollars) per month rather than selling it to you. I'm sure they are looking at the price points carefully and you wouldn't save much. Just a massive reduction in the faff factor.
The watches might be a better bet for money saving - can't imagine those being anything other than direct purchase.
I've signed up for the newsletter now and offered to pake in the beta test of the PKVitality watch although I'm not sure how all those sensors on the back wouldn't irritate your wrist.