The popularity of WiFi networks has been rising rapidly during the last 15 years. In urban areas hotspots are ubiquous. These hotspots together with clever trilateration algorithms provide a cheap way to find out your or someone elses relative location.
While working on Whereami I got interested on how Apple location services work. I know it is
locationd since Little Snitch keeps blocking it. Tinkering with MITM proxy revelealed interesting results.