This just released today. For right now, you can use the demo feature of this app to get an early look at the menus for the game. When the game comes out, you'll be able to control your inventory using this as well as check in with your character even when you're away. The audio in this immediately brought me back to the many many hours I spent with Fallout 3. Just one more excellent marketing move on their part. Hype train!
Report
Hopefully someone builds the "google cardboard" equivalent of this so we can just put our phone into a cheaper, dummy Pip-Boy.
Product Hunt