At about 1:10 in the second trailer for Captain America: Civil War, we see Tony Stark touch what appears to be a wristwatch, which suddenly expands and unfolds into an Iron Man gauntlet covering his hand. Was this invented for the movie, or has it appeared in the comics before?
While this particular device was new for the Marvel Cinematic Universe, Tony has been accessorizing his armor for decades in the comics. The capacity of a watch to activate and become part of his armor actually hails back to the late seventies.
This very device may be an homage to an earlier watch Stark wore to activate an armor suit which was embedded in his chestplate allowing him to turn into Iron Man even when he appeared to be wearing nothing but his underoos.
In every Marvel movie that includes Tony Stark, they introduce a new tech invention to elevate Tony's status. New suits and new accessories are some of them.
In previous Marvel universes and MCU productions, we have seen Tony use portable wrist wear to control his Iron Man suit.
In Earth-199999 universe, MARK VI suit has wrist rockets.
And in The Avengers, Tony uses bracelets to control the suit.
This is only assumption but I can say he loves a good accesory. And there are no comics references for the asked invention, so far (I couldn't find one).