Meet NOLO: a motion tracking solution for mobile VR and Steam with 6 DOF that makes your passive VR experience active. It consists of a headset marker, controllers, and a base station. Just put the base on a table, open Riftcat on your PC, and the Vridge app on your smartphone, fix the headset marker on your headset, and connect the device to your PC.
NOLO has a latency of less than 20ms. You get a tracking range of 13 ft x 13 ft. The battery lasts up to 4 hours. Yet another awesome Kickstarter project.