Enkin  is showing the kind of usage for mobile devices that  excite me. 

What I’d like to see is  an even more  localised version. GPS kinda blows up indoors / concrete canyons  so using this  at  the insides of tradeshows / car dealers    you ma need to   have some low level ( and leakproof)   gps simulator  or wifi that you can triangulate into  a full map of the showfloor. E.g  something more subtle than the SSID  / MAC address on  multi units near your target area.   Wifi is cheap  I wonder how accurate you could get in a room  full of moving bodies with  a few sets.