With Android 4.3 apps would be able to read, discard notifications and even activate buttons in the notification bar. Basically, this grants full access to the notification shade for third-party applications.
Such apps would be called “Notification listeners” and there is even a separate menu te menu that you can access if you have flashed 4.3. In Settings -> Shortcuts -> Settings Shortcuts you’d see a listing for “Notifications”. Tapping on it opens the new screen.
What does this entail? First of all, more opportunities for third-party applications obviously. Also though it could be a hint that Google is paving the way for itself, so devices like a future smartwatch or Google Glass would have deeper integration with Android. Eventually, who knows, this might be the first step toward replaceable notification panels. In either case, we’re looking forward to Google’s official explanation.s
source: Android Police