A few days ago a formal Steam app for iPhone and Android. Unfortunately not everyone could enjoy it: the beta version of the app was only for people who had received an invitation. Less than a week later the app removed from beta and available to everyone. The app contains three sections: Community, Store News. The Store features at first glance all you can buy via the desktop. You can offer in the Steam catalog search, add games to your wish list and then buy them for later download. If you look at the news section, you will find there announcements, press releases and information about new releases.
There is also a link to the Steam forums, a news feed, which is filled by various game sites. But the app will primarily intended to stay in touch with your friends. This is the community component is present. You can chat with friends and see which games your friends play at the time or have bought.
Download: Mobile Steam (free)