VR Tracker is an Open Source 3D position tracking system for Virtual Reality. This device aims at improving VR experiences by allowing the user to move around in a large environnement. It uses at least 2 infrared tracking cameras (PixyCam), which are sending 2D positions of an infrared dot via Wifi thanks to an ESP8266 chip.
Those datas can be processed in a phone or PC using Unity and the OpenCV library to triangulates the position and get a 3D position from two 2D positions.
More info can be found here :