Thanks for the link. I have doubts about its validity and reliability for measuring PWV.

The PPG signal is recorded at the arteriolar/capillary level of the vasculature. Then the wave is mathematically deconstructed to derive the PWV on the upstream arterial level. While it is conceivably possible to do this for a given individual after calibrating the devices against an actual PWV measurement, I doubt very much that such calibration data are applicable across user populations.

The PPG signal is very sensitive to personal and environmental disturbances and idiosyncrasies. That’s why I doubt its reliability.

Even if these problems can be overcome, you’d only be able to derive the PWV of the closest upstream vascular path (brachial-radial) but not the central PWV. brachial-radial PWV is a poor indicator of vascular health.