OK, that's not strictly true (although it could be) but I was just following the Leveson Inquiry and a need to make a vulgar headline came over me for some reason - can't think why.
ANYWAY, IPS (Indoor Positioning System) is a real system that is coming to buildings near you soon(ish). There's a great article about it over at ExtremeTech for in-depth reading, but - in short - GPS (Global Positioning System) is limited in a number of ways. For example, GPS does not work indoors, or penetrate through walls very well (the signal between Earth and satellites is too weak). Neither does it determine altitude particularly well.
However IPS, a system currently being pursued by both Google and Nokia (according to ExtremeTech's article), would enable such capabilities. It's wholly imaginable that someone's personal computing device could switch from GPS to IPS once indoors, and use that data in all manner of new ways (museum guides, floor plans to find offices or shops in multi-level buildings, competing deal hunter apps that know the price of an item over several stores in one building).
It's a crazy thought in many ways - although obvious in so many others. Triangulation via WiFi, personal devices that become connected network repeaters, it's all possible and, I think, likely to be coming soon.