This reminds me of a similar (but visual) project done several years ago, called "Light Painting WiFi" [0], which has popped on HN more than once, most recently in April [1].
Are there any city-wide (or larger) WiFi maps available anywhere? We well know that Google and several other companies have been collecting WAP data en masse for many years, but I don't think I've ever seen much done with the data publicly aside from a handful of this sort of small-scale art project.
Are the data considered too valuable or too controversial by the collectors (cartographers?) to publish openly?