Open source Cardboard SDK and samples
An in-browser implementation of JanusVR
Google Cardboard XR plugin for Unity
Foot tracking algorithm demonstrated in Seb Madgwick's 3D Tracking
Javascript/WebGL lightweight face tracking library
X Inertial-aided Visual Odometry
Code examples for the new features of iOS 7
High-precision indoor positioning framework for most wifi devices
Software for motion tracking (skeletons, objects, hands) via Kinect!