We loaded the up the hefty (612MB) app and, for some reason, had to inform it the Xbox One's IP address (accessed via Settings -- Network -- Advanced Settings), because it wasn't automatically detected on the network. Once connected, the main screen on your mobile device offers access to a wiki about the game and to your all-important personal stats. It's only when you load up the game on your console that the second-screen function kicks in, showing a zoom-able live map of the entire arena, including the names of players on your squad.
EA Mobile reckons the extra info on this map could give second-screen users an advantage, but for this writer it was more of a distraction, and it was quickly forgotten about in the midst of an overriding desire to not get killed in the "real" game playing out on the main screen. If you have any tips on how to actually make use of this thing, do us all a favor and them in the comments, otherwise we'll just have to hold out for compelling second-screen app for a slower-paced game.