i have this scale.
its actually been discontinued in most countries (with one around the same price point with more features). probably good price deals on it.
regarding your question, it measures the time it takes for blood pumped out of the heart to reach extremities. it calls this a measure of your vascular age.
in terms of function, it compares itself (on its website) to a blood pressure monitor.
its data gives 3 general categories: optimal, normal, not-optimal.
i have better than normal blood pressure for persons my age when measured by a blood pressure gauge but i am not an athlete. withings rates me as normal.
in terms of body mass percentages, specifically for bone mass, the data do co-relate to my annual health checks.
for me, although withings' upper end scales do have some interesting features, the main reason why i use it is because of the withings iPhone Health Mate app. this app is all that i hoped apple Health app would be.
it turns out that the direction that apple has taken for its Health app is to be the data repository for health info. leaving interpretation and info usability to other companies, with only basic quantitative trend data.
the withing's app uses my apple watch info including the workout (run and walk maps) data, etc etc. and combines available info to give me better summaries and trends than the apple app. it also uses the same data and gives a slightly different outlook on what is happening trend wise, etc. much like would happen if you go visit two different doctors.
after withings bought back its brand (!) from nokia (which almost trashed it), its really the leader in my opinion.
