Company president and co-founder Gabe Newell said the app comes at the request of many fans over the years -- it marks Valve's first foray into the mobile space. "Mobile is changing the way people interact, play games and consume media, and the Steam app is part of our commitment to meet customer demands and expand the service functionality of Steam to make it richer and more accessible for everyone," Newell said.
No news is given regarding the potential for iOS or Android game selling through the Steam mobile portal, but it seems unlikely -- at least on Apple devices -- given various terms of service restrictions regarding competition with the official application stores. Both the Android and iOS versions are available as of right now.