By the way, this same information is already tracked and stored by the mobile networks themselves, and can be obtained by the government with a warrant (or like

By the way, this same information is already tracked and stored by the mobile networks themselves, and can be obtained by the government with a warrant (or likely by organizations like the NSA or CIA without one, given recent precedents). See http://nce.fd.org/PDF%20Cellular%20Tower%20Location%20Information.pdf http://nce.fd.org/PDF%20Cellular%20Tower%20Location%20Inform... : "Cellular service providers generally retain information about phones’ contacts with towers, including which tower(s) each phone contacted during any given check-in, and which “face” of the tower(s) the phone contacted."