Steam Machines hardware today, Valve pulled back the curtains on a related beta program. The program will grant 300 lucky testers access to prototype hardware for free.
In order to be eligible for the program, players must first join the Steam Universe community group, agree to the beta program terms, obtain ten friends on Steam if they haven't already, create a public Steam profile and play any game in Big Picture mode. Valve says the steps can be performed in any order, and your eligibility status can be tracked online at any time on your "quest page." The eligibility list locks on October 25.
Update: Valve's final announcement, made on Friday, is the Steam Controller.