If you are a a developer and want to cross platform your game play, Amazon today announced that it had made its (not a copy of GameCenter) GameCircle available to iOS developers.
Amazon GameCircle and Whispersync for Games is live on iOS and Android! You can store game data in the AWS Cloud so players don’t lose their game progress, high scores, or achievements when switching between devices. We know programming for multiple platforms is standard practice for many developers—iOS support has been a frequent feature request—so we’re excited to make GameCircle available on a whole new class of devices. GameCircle and Whispersync are free for you and your players. Plus, when you integrate GameCircle achievements, you automatically get access to Achievement Reports as well. These reports help you get a better understanding of how players interact with your game so you can make sure they’re having a great experience.