I hacked up a quick head-tracking solution one weekend using my phone and WiFi. The problem was passive calibration. Accelerometers and gyroscopes are noisy and imperfect. Drift occurs and without the Occulus tracker or Vive lighthouses you are in for a frustrating experience.

I own a DK2 and for many concrete reasons disagree with the author, it is not a novelty. Phone-based stuff is most certainly a novelty.