You could attempt to time round-trip signal latency directly or via interference patterns, but it's a much shorter timescale. Light travels just shy of 1 billion feet per second, so we're talking differentiating in the 10s of nanoseconds, which requires nontrivial components.
I already posted this link in the epic nope thread that is a sibling to this one, but the paper linked from Wikipedia speaks of an experimental implementation with a return time of 1 ns:
There are papers going back to at least 2005 (this one, a top search result, is cited 390 times: http://www.cl.cam.ac.uk/~mgk25/sc2005-distance.pdf ), so it would not be all that surprising if there are some existing commercial implementations. The current rash of thefts seem to come down to the systems being completely naive to amplification attacks though.
