Interesting. According to an announcement posted earlier today, Valve has implemented support for Razer's Hydra motion-sensing controller right into Steam. Here's the skinny from the press release:
Sixense and Valve have now integrated Sixense MotionCreatorTM 2.0 software with Valve’s Steam gaming platform, enabling backward compatibility for motion gaming with the Razer Hydra for over 250 of the most popular titles on Steam. Now, Steam users will receive automatic motion control updates for current and future game titles, and a new in-game overlay allows gamers to view control maps for the Razer Hydra as they play.
Considering the rumors we discussed this morning about Valve building a "Steam Box" hardware ecosystem for the living room, this development seems particularly notable. Oh, sure, most PC games these days will happily accommodate an Xbox 360 controller, so Valve wouldn't exactly need a unique input device for the Steam Box. Still, the Hydra does things the Xbox 360 controller can't do, and at $99.99, it's not an outlandish proposition for a living-room gaming PC—provided in-game support is solid, of course.
In related news, Razer says three Valve titles—Left 4 Dead 2, Half-Life 2, and Team Fortress 2—now have "fully integrated motion gaming support" with the Hydra. (That's in addition to Portal 2, which was already supported before.) Future Valve titles, including Dota 2 and the new Counter-Strike, will also have native support for the controller.