The article describes some circumstances under which a cell phone can be more precisely located.<p>> Similarly, if you make an emergency 911 call, your company will use three towers to triangulate your location; if you’re using a smartphone, it will use G.P.S. to pinpoint where you are. If you’re the target of an ongoing investigation and law-enforcement agencies want to track you, they can ask a phone company to “ping” your phone in real time.<p>The “ping” part caught my attention: this sounds like a method that actively queries the phone in a way that could be detected by the end user. Does anyone know if this is possible to detect? Would, for example, an Android phone allow a developer to write an app that could detect this and notify the user?