It's basically common knowledge that Valve is working on hardware. With numerous job listings and hirings for hardware developers and a hands-on with their new piece of hardware, the fact is that Valve, who almost singlehandedly changed the distribution of PC games, is putting its fingers in the console pie. Now, it looks like they want you to help playtest it.
Valve is now letting you sign up to playtest "released and unreleased versions of [their] games as well as play around with some of [their] hardware prototypes." This means, if you're lucky, you'll be able to get your hands on the gaming headset Valve has been developing, similar to that of the Oculus Rift, and get a chance to play some (released and unreleased) Valve games like never before.
The survey (available below) asks you to simply fill out some information on your experience as a gamer, as well as some questions pertaining to motion sickness. Most of these headset devices do bring motion sickness as a side effect, so this seems like a common question.
Sign up below and give it a shot. Maybe you'll play Half Life 3.
Source
Playtester Survey and Sign Up