Steam News announces they are selling the Razer Hydra PC Gaming Motion Sensing Controller, a PC peripheral providing motion control (this was mentioned last night, but seems worthy of more notice). This is a $139.99 unit that comes with a free copy of Portal 2 as well as the Portal 2 Sixense MotionPack DLC, and it is not clear if this DLC will be released for the rest of us, but it seems unlikely from the gameplay trailer, as the DLC clearly makes use of some new game mechanics. Here's word:

"The Sixense Portal 2 MotionPack™ is custom-designed for use with the high-performance Razer Hydra motion tracking controllers. The MotionPack was designed from the ground up to provide the most advanced and immersive motion control experience ever seen. Reach, rotate and scale your way through both Portal 2 and the exclusive MotionPack test chambers. Intuitively interact with Portal Test Chambers using the Aperture Science Handheld Portal Device in full three dimensions; fire portals at precise angles and throw Weighted Companion Cubes with measured force."