iOS 7 was Apple's first attempt at going for a flat style when it comes to the UI. I personally am not a fan of the design of iOS 7 because it seems unfinished. But as with any major OS, Apple is continuing to improve it.
Bill Labus took out the time to make his own concept for a feature he would have to see in iOS. iOS 7 brought with it control center, where users could easily access common settings for their iPhone. Bill has come up with an idea to blend both the control center and multi-tasking function together in one place. Instead of double clicking the home button to open up your most recent apps, this concept allows you to swipe up from the bottom like you normally would with control center. There would then be no need for the double-clicking to access your most recent apps.
Not only is the UX fantastic, but the UI design itself is amazing too. It's a very nice blend between flat and realism, with subtle shadows, buttons and cards.