I prefer changing the battery once every three years over having a radioactive emitter strapped to my wrist. There is a decent case for nuclear pacemakers since changing the battery of those requires surgery, and even there it didn't get traction. Watch batteries are quick to change, I don't see the risk/benefit tradeoff working.
And with smart watches we are back in "useless for most applications" territory.
And with smart watches we are back in "useless for most applications" territory.