This feature is currently in the "preview" stage, and is only available to Xbox Insiders residing in the United States and the United Kingdom. With Xbox Console Streaming, you will be able stream/play any Xbox One game that is installed on you console to an Android device (i.e. a smartphone or tablet). Xbox Game Streaming isn't limited to titles you own either; it also applies to any game that you have installed via Xbox Game Pass. While backwards compatible Xbox and Xbox 360 aren't supported, that functionality could arrive at a later date (Microsoft is being cagey about this point).
This is a big boon for Xbox One games that want to take the action on-the-go with their smartphones, although you'll need a stable internet connection to avoid any lag or lapses in streaming quality. Microsoft requires upstream bandwidth of 4.5 Mbps for your Xbox One console (9 Mbps preferred) and network latency of 125 or lower (60 ms preferred). Your console's power setting must also be set to Instant-on.
"This preview is an important step in our journey to deliver game streaming to Xbox players around the world," writes Microsoft Principal Program Manager Jonathan Hildebrandt. "We’ll work closely with you and the Insider community to gather feedback that will shape and define future iterations of Xbox Console Streaming."
In addition to needing to be on the Xbox Insider Alpha or Alpha-Skip-Ahead rings, you will need a phone/tablet running Android 6.0 or higher, Bluetooth 4.0 or higher, and a Bluetooth-enabled Xbox One Wireless Controller. You will also need to download the Xbox Game Streaming (Preview) app on your mobile device.