The My Xbox Live for iOS devices is out now, free and optimized for either iPhone/iPod Touch or iPad.
With My Xbox Live, Xbox gamers can manage and alter several facets of their accounts. From the iTunes app description:
“Take your Xbox LIVE experience wherever you go with the My Xbox LIVE app. Track and compare your achievements, connect with your Xbox LIVE friends, and change up your 3D Avatar. Review all your recent great games you and your friends love to play and compare achievements with them. Jump into our games hub to learn about the latest LIVE games and apps. Access Xbox Spotlight feeds, get breaking news from Xbox LIVE, game tips and tricks, gamer spotlight and much more.”