Valve's Steam Link app - a beta version, at least - has rolled out onto Android, with an iOS version soon to follow. Now folks with any kind of modern tablet, phone or other free-roaming screen will be able to play their PC games library anywhere in the house through the power of low-latency video streaming, assuming your home Wi-fi is up to par.
You'll need a relatively recent phone or tablet to get the most out of this, and ideally a Steam Controller or two (which recently was updated to play nicer with iOS), but at the price of free, it's hard to complain.
The most surprising thing is that the Steam Link app works at all for me, given my cheap and ageing Android phone and its unwillingness to pair with any Bluetooth controller that I own. Despite these setbacks, the app does seem to work nicely, although I'm not sure whether to chalk up stuttering video to poor local Wi-fi (I do most things via Ethernet) or just my phone's underpowered CPU not being able to keep up with the sheer volume of data. I still managed to play few turns of Battletech using purely touch-screen controls, which feels borderline magical.
Folks on less terrible devices (including our own Graham Smith) have reported that it works genuinely well, at least when paired with Valve's own Steam controller, which I lack. While there is a frame or two's worth of input lag, it shouldn't be too much of an obstacle to playing most games, and apparently Apple TV owners can shave that latency down even further by just hooking their streaming device up to Ethernet as well. All in all, it does what Valve's standalone Steam Link box did, just with fewer cables (and fewer USB ports, admittedly), and that's a good deal for free.
The Steam Link app is free and live now via Google Play. It'll be arriving on Apple's iOS app store soon, with an Apple TV version soon to follow.