Here are some kids report on using the technique we were talking about. Resolution 5 meters. Not what we want. But read the discussion after the article.
I did some more calculations, and it looks like we'll need about a 2GHz chip to get resolution less than 1 foot. Probably faster. I just want to get the proof-of-concept working, then we can attach the radio to an ASIC or something for higher resolution.
Those kids did good work.