Actually it hasn't proliferated into civilian use because the military industrial complex has captured pretty much anything with real accuracy.

I had an old colleague who in a previous life worked on an incredibly accurate positioning system that was effectively a brief case that knew where it was at all times. The story he told was the DoD made them an offer they couldn't refuse, and everything became secret. I'm pretty sure the company in question is still in business.

I'm not trying to say it's not legal but it might not exactly be legal?