At the moment, this isn't standard equipment for umpires; only Bruce Oxenford is using it at the moment as far as I'm aware. As such, I'm guessing this is a personal piece of equipment that Oxenford is using and as such it doesn't have a formal name, but yes, it's obviously for the umpire to use as protection from the ball.
For what it's worth, this isn't the first time Oxenford has used the "shield" - he also used it in the Australia vs West Indies World T20 warm up match earlier in 2016.