This is an interesting read on how the guts of iOS 6 have changed to use XPC for system-provided controllers:
In my previous article on sharing in iOS 6, I hinted at the possibility that Apple was working on a more powerful method to enable sharing between apps without compromising the iOS security architecture.
In fact, Apple is already using a new undocumented concept called Remote View Controllers in iOS 6. This post is an attempt at investigating what is going on under the hood in iOS 6 and what this may mean for future versions of iOS…
Also, a couple interesting tools from the footnotes:
Pimping recursiveDescription to include controllers as well as views.