BannerDisable is a jailbreak cydia tweak, which enables the user to toggle banner notifications on/off. This feature was added in the new iOS 6, which releases later this summer. So if you want to get a taste of some of iOS 6 features try out bannerdisable. This is a free tweak available in ModMyi repo. It adds a toggle under the settings menu to disable notification banners. It does a great job from what I have seen so far. I recommend you try it out.