I've been playing this on Steam for the last couple of days and am having a blast.
http://store.steampowered.com/app/588430
All the little cartoon characters from the Fallout game run around using all your favorite objects from the games. You build a vault, try to keep your people powered, fed, watered, reproducing, and happy. It has tablet written all over it, but it's fun.
It's Free-to-Play, and if you really insist on wasting money you can buy lunchboxes to speed things up, but there's really no need.
This has apparently been out for a year or two outside of Steam. I vaguely recall hearing that it would come into existence, but didn't pay it any more attention.