Now, I can see wifi signals
That is slick. The wavelength of 2.4Ghz radio being 125 mm and 5Ghz being 62.5mm it looks like he is imaging standing waves in the 5Ghz spectrum. (if the cube is 360mm x 360mm it would have ~6 waves of 5Ghz and ~3 waves of 2.4Ghz RF energy. There is an experiment to see the standing waves in a microwave using chocolate - http://morningcoffeephysics.com/measuring-the-speed-of-light... which demonstrates the same sort of thing, but frankly I think this is much cooler.