Combine this with the Meta Pixel illegal localhost tracking that bypasses privacy measures [1] [2] and the privacy leaking could be off the scale.

I think this goes for all things - medical data such as heart rate, blood sugar, steps, weight, VO2 max, etc, could all be seriously misused.

Personally I try to use apps that are not cloud-based, or make my own, but this isn't an option for everybody.

[1] https://www.zeropartydata.es/p/localhost-tracking-explained-...

[2] https://news.ycombinator.com/item?id=44235467