One of the big announcements coming from Valve is that the game publisher will offers its VR tracking interface on a royalty-free basis. This means hardware makers will be able to buil trackable sensors into hardware for VR games, without having to pay money to Valve for use of the technology. Full details at ARS Technica, which details some of the restrictions of the license program.
If a hardware maker wants to create physical objects that will interface with SteamVR—like a pair of gloves, a two-handed shotgun, a piece of fake medical equipment, or whatever else you can imagine—the object in question needs to be tracked by the system's "room-scale" pair of infrared boxes. The HTC Vive's headset and wands play nicely in VR mostly because they're each covered by dozens of IR receiver dots. The headset and wands are spread out in such a way that, no matter how you hold or use them, one of the Vive's two tracking boxes can be seen by enough of the IR dots.