I wonder how this would fit in in countries with universal healthcare?

This is a natural fit for the US, where the business of healthcare happens much closer to (and often involves) the end consumer.

In countries with universal healthcare, I think this would only work if Facebook/Google/Apple made the state provider the first choice to receive healthcare data. The state normally has programs in place already to centralise and analyse health data and what Facebook are proposing is essentially setting up equivalent functions in parallel.