According to sources, the company has been working on a hardware spec and associated software which would make up the backbone of a "Steam Box." The actual devices may be made by a variety of partners, and the software would be readily available to any company that wants to get in the game.
Apparently meetings were held during CES to demo a hand-built version of the device to potential partners. We're told that the basic specs of the Steam Box include a Core i7 CPU, 8GB of RAM, and an NVIDIA GPU. The devices will be able to run any standard PC titles, and will also allow for rival gaming services (like EA's Origin) to be loaded up.
Mostly just speculation at this point, but it's an interesting article regardless.