I did this for my senior design project a few years ago.

We had 4 raspberry pis with mic arrays. They were time synced over a wifi mesh network (indoor so no GPS). Each had a detector running, and would send detection segments to a base station to run generalized cross correlation.

It worked pretty well, but we were doing it in room scale 20' environments. Our biggest issue was that we could not disambiguate echos, and had to hack in a hold off period.

We did not end up having time but I wish we could have gotten beamforming working on each pis microphone array, then we could have combined angle of arrival with tdoa, and potentially better handled the echo.