The way to measure PWV is to either measure the arrival of the pressure wave at two different locations (e.g. carotid and femoral) or to record it at a single site but gated to the ECG signal. In both cases you need to know the distance between the two measurement points, respectively the heart and the single point.

There are several clinical devices to measure PWV (I had been involved in the development of one such device), and there is one device that makes the measurement accessible for laypeople: The Withings Body Cardio scale, which I use for my clients and our DIY lifestyle medicine application. I have no financial ties with Withings, I'm using their technology simply because it's the only one for laypeople on the market, and it has been independently validated. The technology behind this scale is called ballistocardiography. You can read up on it on the internet.

PWV is determined by the radius of the artery, the wall thickness, and the elastic modulus of the wall (the latter being a function of the pressure, too). Hence, PWV gives us a good estimate of the functional health of the artery.