"Even if medical privacy laws did cover data recorded by a Fitbit band, it wouldn't matter, Reitman said, because there's an exception to HIPAA for law enforcement queries, national security and many other legal requests."
To me, this sound like even X-rays, EKG results, MRI or CAT scan results or even just doctor's notes could be at risk. So, if an insurance company thinks you are lying about your disability claim, they could ask law enforcement to grab up the X-ray of that broken ankle you suffered playing in the beer softball league.
You don't need a wearable for any of that.