The HTC Vive’s Lighthouse localization system is one of the cleverest things we’ve seen in a while. It uses a synchronization flash followed by a swept beam to tell any device that can see the lights exactly where it is in space. Of course, the device has to understand the signals to figure it out.
[Alex Shtuchkin] built a very well documented device that can use these signals to localize itself in your room. For now, the Lighthouse stations are still fairly expensive, but the per-device hardware requirements are quite reasonable