Poor OBJ. So wanting attention, so wanting to monetize himself as a billboard on the field and his thunder is stolen by Antonio Brown.
If its metal its a hazards. If it is plastic and capable of being shattered into shards, its a hazards. If neither, it is precedent so that other guys can seek to violate the uniform policy wearing things maybe for which they can get paid, causing a distraction. Reminds me of Jim McMahon and his headband 35 years ago. the league has licensing deals with shoe companies and athletic apparel makers. Those deals are based upon a clean, undistracted look, a look not competing with other products on the player's bodies during games. He should no more be able to do this than a ref should be able to review a play on a Mac book instead of the surface tablet they are authorized to use. The stage belongs to the league, not the players. The players get to share in that revenue, but they do not get to set the rules. they don't get to carry phones, sharpies, or wear designer watches. Some wear ear rings or neck chains, there is precedent for that but even that would be curtailed if it became distracting.
If he tries to take the field in out of uniform he should be prevented form doing so and should get a uniform fine, just like his jersey was untucked or his socks too low. Remove the watch and then he can be allowed to enter the game. Is this the man coming down on him personally, nope, the policy goes to everyone and benefits everyone both as a safety issue and by creating large endorsement dollars from the approved licensees, endorsement dollars that go into the cap pool which benefits everybody, even self important jerks, like OBJ.