Not just medical insurance companies. But that will come when wearing of these devices are made mandatory, probably an argument along the lines of "well only terrorists *wouldn't* wear them"
You say that like the edict will come from the right wing, and that may be a popular belief. But the left is the party that voted to mandate health insurance, and people went along with it because, a) they believed the "it's for the good of everyone that everyone have insurance" line; and/or, b) they accepted it because it came from their side. Granted, the established left and right in the United States is basically the softest game of tug-o-war in history; however, it seems to me that the "Fitbit Mandate" will come shrouded as "it's for the good of everyone that everyone have a Fitbit" rather than "The Gestapo says you will wear a Fitbit."
People wouldn't willingly concede even more freedoms to wear these things, you say? Yeah... right.
Sadly/Generally, the average person will follow along with what their chosen Party says they should do.