This rumor comes from Steam forums' user Political Gamer, who says he went to visit Valve HQ recently and spoke to boss Gabe Newell. While speaking with Newell, he learned that Steam will get a video recorder "very soon" and that the company is "looking into the iOS/Android platform for possible expansions with Steam."
We don't know how accurate the information is, but we are sure that if any of the story was inaccurate that Valve would have immediately cleared things up given that the post in on their official Steam forums and has already received widespread attention by the gaming sites.
Again, this is wasn't officially mentioned, and even then, Newell said Valve was "looking into." That can mean anything at this point as far as where Steam integration to mobile platforms can go, if at all.
Steam is a digital distribution service for games. The service is provided by Valve, the folks responsible for the Half-Life and Portal series. However, the games on Steam are not limited to Valve's library.
It will be interesting to see if the service is expanded to iOS and to what extent. That said, we are betting that this early in the game any sort of official announcement is still a little ways off.