Holy crap. While demonstrating Fallout 4 at E3 2015, Bethesda announced an iPhone game you can download today.
It's called Fallout Shelter, and in it you are the Overseer in charge of your very own vault.
You bring people into the Vault, assign them tasks, level up their specs, send them out on missions and grow the community.
The best part is that it's completely free, and features almost no in-app purchases. The only in-app purchases you can go for give you more loot drops according to Bethesda.
Clearly Fallout Shelter is designed to keep us all occupied until Fallout 4 lands on consoles and PC in November. I'm already sold.
You can download the game for iOS right here.
Check out some screens below: