No, I am not referring to Xi3's Piston. Steam Box itself is a separate console under development by Valve, within the next three to four months Valve plans to have prototypes shipped out for testing so they can get some feedback.
In a discussion with the BBC, Gabe stated:
Gabe Newell wrote...
“We’re working with partners trying to nail down how fast we can make it… There are noise issues and heat issues and being able to [deal with] that while still offering a powerful enough gaming experience is the challenge in building it.”
The major item holding up Valve's development are their controller prototypes, they have a few to choose from and I'm okay with waiting a little while longer for them to hopefully come to a good conclusion and give us a new controller on par with or more advanced than the PS4's controller. What might we be seeing in the new controller? In the same discussion, Gabe also stated:
Gabe Newell wrote...
If you think of a game like Left For Dead – which was trying to put you into a sort of horror movie – if you don’t change the experience of what the player is actually feeling then it stops being a horror game. So you need to actually be able to directly measure how aroused the player is – what their heart rate is, things like that – in order to offer them a new experience each time they play.
While I bet some people would be put off by this, I think it's a great idea. To think of the amount of expressional power you would add to a developer's arsenal through the use of biometric feedback is quite something. Your very own emotions controlling the kind of game play you experience, triggered storyline events, how NPCs react to you, visual feedback and more. I think the use of biometric feedback just might be "the next big thing" and what will really set the Steam Box apart from the rest of the crowd. If anything, it probably gives Sony & Microsoft something to think about the new fish in the console pond.