There is wide variety if approaches that could be utilized for tracking.
Laser Tracking as per valve's design (steam)
Optical tracking; ie msmr style. & Hand modul.
-Greg from Driver4vr has been working using Leap Motion as some kind of roomscale. @jonnypanic has said Leap still needs a lot work if mem serves.
Wi-Fi triangulation? (A user posted an article)
GPS based tracking (read an article awhile back).
Simple Truth PiMax will develop their own tracking at some point. But with the idea of modular design means other devs can create their own tracking ideas & have them supported potenially native.
Case in point could use echo locate sound waves like a bat if a developer wants to.