For example, in another comment, I mentioned a study that's using the Oura ring, which is a great product, but has a far smaller user base than the mass-market Fitbit and Apple Watch audience that our study is focused on. So it's really additive to have both of our research efforts going forward.
ABC7 in SF just reported a collaboration as "Stanford and Fitbit", giving innovators.stanford.edu (not working) as a site to sign up. Relatedly I find the following:
https://hitconsultant.net/2020/04/14/fitbit-scripps-stanford...
I could imagine participants in any device-specific work opting-in to sharing anonymized data with one-or-more broader-based studies/analyses, if that is not part of opting-in to the device-specific work in the first place.