PopKey, the GIF keyboard, is now in the Apple App Store
To refresh your memory, the free app replaces letters on your keyboard, with GIFs that you can use to illustrate what you're trying to say. The app also comes with thousands of animated GIFs that you can use in lieu of words. And you can even create your own images to use.
They say a picture is worth a thousand words. PopKey shows that this is true. Who wants to read "LOL" when they could see the Joker guffawing on their screen. Because iOS 8 is the first version of Apple's mobile operating system that supports third party keyboards, you need your iDevice to be running iOS 8 or higher. There is still no word on whether we will see a version of PopKey for Android or Windows Phone.
source: PopKey (iOS)