FIFA 17 Companion isn't a game itself -- instead, it's a free utility that helps you keep track of what's going on in your FIFA 17 game. If you want to stay on top of Ultimate Team mode's transfer market, you can use the Companion to pick up player transfers, change formations and visit the shop from your mobile device, meaning that as soon as you sit down at your console or PC you can jump right into a game.
Managers work around the clock
FIFA 17 Companion is easy to use, although getting it set up requires logging in to your game, creating an Ultimate Team mode club, creating a security question and then logging in from your mobile device, which is a somewhat convoluted process. In addition to managing your club, the app can also help you develop it by earning coins and packs. Squad Building Challenges are minigames in which you build squads to meet certain requirements. Do them and you'll earn rewards to help you build up your team.
Control your game
If you're very invested in Ultimate Team mode and you'd like to be able to do your club's admin work and shopping no matter where you are, FIFA 17 Companion is a useful tool. If your main focus is on other areas of the game, you'll find it less useful.