One of the fancy features promised by SteamOS is the ability to stream Windows games over your home wireless network. So even if you don't have a top of the line Steam Machine hooked up to your TV, you'll still be able to use your primary gaming PC to stream Windows games wirelessly.
The feature has now entered beta, and is primarily directed at "development partners." (via PC Gamer) However, "more and more people" will be invited into the beta over time. In fact, it appears that many non-developers are already getting access.