According to a South Korean news site, Samsung has launched a patent-infringement lawsuit in Korea against Apple over the iOS version of Notification Center, saying it violates their patent. The feature, which debuted almost two years ago, is also similar (but not identical) to an Android feature called Status Bar for which Google recently received a US patent. Apple most recently brought the Notification Center over to the Mac in OS X Mountain Lion.
The Samsung patent is not believed to be a "standard essential" implementation of the idea, unlike most of the patents the company uses in its war of litigation against Apple. It's unknown if the patent Samsung is asserting is one of its own or the one Google now holds for similar technology. Apple's implementation of the basic concept is somewhat different from either Samsung's or Google's version, for example featuring Facebook and Twitter integration by default, but is unmistakably Apple's own "take" on a concept that first appeared on Android phones.
Notification Center can show updates in email, Messages, texts, weather, calendar events and individual app alerts through a drag-down screen that is universally accessible on iOS devices. Users can "customize" the information shown by choosing to allow or disallow certain apps to show alerts in the Notification Center through preferences. It is not yet known specifically what part of the existing Notifications Center Samsung believes is in violation, though it is unlikely that the company tried to warn or offer licensing terms -- as Apple famously did before suing Samsung in US court -- prior to filing the lawsuit in South Korea.