Extensibility on Android KitKat vs. iOS 8

I am not an android user. In fact, the only time I've ever played around with android is at a Verizon store. I've been using iPhone since day 1, and once apps were introduced, I always wished they weren't so sandboxed.

iOS 8 introduces "extensibility," which allows apps to communicate with each other. But Android users have been commenting "we've had this for a long time." But from what I've heard, android has something called "contracts and intents" that allow apps to launch files and links using other apps. This seems like a really basic form of extensibility.

From what we saw in the iOS 8 keynote, apps can introduce share sheets that let users shuttle around files and links like Android...but so much more. From what it looks like, an app can almost create like a mini-app with limited functionality that launches, when appropriate, inside another app. Like an app within an app. This opens up limitless possibilities and functionality that was only possible on a desktop OS before.

My question is to android users: does android allow for this "app within an app" extensibility in its contracts and intents system? Or does it seem like iOS 8's "app within an app" version of extensibility is more complex than what Android currently has in KitKat. Curious in what people who actually use android and ios think.