Valve is releasing Steam Link apps for iOS and Android sometime during the week of the 21st of May. They’ll stream games to your device or TV from a host computer just like the Steam Link box does. Valve says that these apps will support a few different types of controllers including Apple’s MFI standard, but I’m not sure how they have Steam Controller support working without attaching the full-size USB type A dongle, unless they intend for people to use a series of adapters.
The physical Steam Link box could still end up being useful by working with even more types of controllers, as well as running general purpose software using the Steam Link SDK.
Valve is also putting out an app to watch any videos purchased on Steam, because that’s a thing people do?
It’s a shame that game streaming is exclusively the domain of stores like Valve’s Steam and Nvidia’s streaming built-into their Geforce graphics cards. Although the latter has some open source support via the unofficial community-developed Moonlight project, neither option is perfect. Steam streaming is often broken for many games outside of Steam, and Nvidia only officially streams to their Shield tablet and set-top-box devices. If you’re using an AMD or intel video chipset they aren’t supported by Nvidia, either.
I’m not sure if there’s any room for a commercial third-party solution when Nvidia and Valve’s solutions work almost well enough, so it might have to be a community-developed open source project.