Whatever happened to UWB? Ten years ago, there was so much talk about UWB, and how it would provide so much bandwidth, etc. And now it's nowhere to be found. One huge advantage of radio is that it can work through walls; "Li-Fi" won't.
If I remember they ended up using it in some system for firefighters that can 'see' through walls, and it might've been used for such a system in the army as well.
But overall UWB didn't deliver on it's promise.
PLUS is an offshoot of Time Domain, http://www.timedomain.com/. Time Domain does radar; I don't think they do any active tracking (could be wrong though). IIRC Time Domain is the company that did the see-through-walls system.