It's a mechanical bird for the Falcon. In the comics, Falcon has Redwing, a falcon Sam bought in Rio, and has been in the comics as far back as Captain America Vol 1 #186 (June, 1975), as old as Falcon himself.
They even have a mental link:
As part of a plot against Captain America, the Red Skull uses the Cosmic Cube, a creation that allows its user to alter reality, to mentally fuse Wilson with Redwing, creating a "super-normal mental link" that would, with time and concentration, give Wilson broad powers over all birds.
Like all magical animal sidekicks, Redwing is also part of the Pet Avengers, along with Lockjaw, and Throg.
In Captain America: Civil War, Redwing is now a drone. As screened to the D23 audience in August 2015:
11:21 a.m. Here’s what we see: The new Avengers are in buildings overlooking a crowded market in what appears to be a third-world country. “Eyes on target, folks,” Captain America says. Falcon says, “Red Wing, launch,” and a small drone hovers free and dives down to the street, swooping beneath a truck, which is loaded with explosives.
So it's importance is really fan wank material. Redwing is as old as Falcon, and just as important to the character as the shield or Bucky is for Cap. Adding Redwing is a nod to Sam Wilson's comic roots, and doesn't detract from the story.
It likely won't be too critical to the plot though. Like most of their powers, it will probably get one scene and then not seen again. Correction, Redwing was used in the big fight scenes, at the beginning and during the TeamCap vs TeamIronMan brawl, to great avail, and mentioned many times. Redwing has sensors, cameras, remote targeting, a grappling hook, missiles/bombs/guns.
If you notice, Redwing is in most of the promo pictures.