Back in October of 2014, a new beta app called Snowball was released. Back then it was a chat head-style multi-messaging client of sorts, which was useful enough in its own right. Snowball 2.0 is out now, and the app has apparently gotten a full overhaul - it's essentially a completely different thing now. Instead of being a messaging client, Snowball is now a full-featured (and damn good-looking) notification center. Check it out:
If I said this didn't look pretty useful, I'd be lying.
There has been a lot of interest of late in a patent filed (by Google) back in 2009 for what is obviously a rendition of Android's notification bar system. There are a number of pretty (well, as pretty as black and white gets) figures in the patent showing the notification bar we all know and love, and lots of language about notification systems and the like.
As many of the Android-faithful know, Apple recently implemented as part of iOS 5 the "Notification Center," and it looks an awful lot like Android's in some respects.