They can do this already, even without GPS.<br><br>The cell company software can measure the signal time delay from your phone to each cell that is 'visible' to it, do a little math, and calculate exactly where you are. With frightening accuracy. It doesn't matter if you are making a call or not; the phone has to intermittently 'chat' with the network to let it know where it is (so that calls can be routed to the right cell).<br><br>Primitive versions of such tracking have already been used as evidence in court cases, demonstrating that the defendant's phone (and hence, maybe, the defendant himself) was at a certain location at a certain time (or, alternatively, *not* at that location at that time).<br><br>The only time they can't pin you down exactly is when you are not visible to more than one cell (e.g. in the sea, or countryside). That's where the GPS is useful.<br><br>If you don't want BigBrother to know where you are, switch your phone off. Better still, remove the battery. Better still, don't take the phone with you.