The new IOS extensions are Apple’s way of trying to meld their walled garden gear into the Internet of things. Essentially Apple has to poke more holes in the garden walls if they want their devices to stay relevant and useful in the coming home constellation of other devices and applications that must interact, talk with each other, and most important – know their context and their user’s context, in order to provide best utility and “artificial AI” semi-aware functionality. The real challenge is to keep those holes secure while functional.
Standards will evolve for this eventually…
Explaining iOS 8’s extensions: Opening the platform while keeping it secure | Ars Technica
Allowing third-party apps to communicate with other apps is just one of the problems extensions are meant to solve—third-party keyboards, connecting apps to cloud services other than iCloud, and the new Notification Center widgets are all their own kind of extensions.
Not all parts of iOS can be changed (or “extended”) by third parties. If you wanted to replace one of the default apps with your own or add some kind of toggle to the Control Center, you can’t do that. Apple defines a handful of pre-set “extension points” to show developers where they can add stuff. The iOS 8 extension points are as follows: