VR headset position tracking using just a printout and a smartphone !
Print and stick given pattern to your GearVR or Google cardboard and this app will track it in 3D using your old/spare smartphone for viewing point cloud stills or videos.
See further details at: https://github.com/Samsung/ColorPatternTracker. This app is referred to as the Tracker app.
Please note the "pattern printing instructions" for printing the app and "Direct installation" for installing and running the VR app on Gear VR or Google cardboard.
Use the bluetooth library or VR apk or Unity GearVR scene in github repository to receive the 3D coordinates and use them appropriately.