The room-scale features lets VR users move within a real space by 3D mapping the room. By adding that third sensor, games and other content should be more immersive because you can wander around in an area while wearing an Oculus Rift.
Adding room-scale support and putting extra sensors on sale isn't that big of a surprise. Back in July, Rift's Oculus Home software gained support for multiple sensors. Oculus isn't the first VR company to add this feature, either. The HTC Vive already supports 3D room-scale that developers can already add to their games.
Both the Touch controllers and the extra sensors will launch on December 6th for $199 and $79 respectively. In total, the full Oculus Rift hardware package (with controllers and environment sensors), will set you back $877, while HTC Vive's similar hardware family remains priced at $799. Decisions, decisions.