From the website http://www.travelbygps.com/articles/tracking.php:
“Stimulated by the events of 11 September 2001, the demand for enhanced 911 (e911) emergency calling capabilities, pushed forward GPS tracking technology in cell phones. At the end of 2005, all cell phone carriers were required to provide the ability to trace cell phone calls to a location within 100 meters or less.
To comply with FCC requirements, cell phone carriers decided to integrate GPS technology into cell phone handsets, rather than overhaul the tower network. However the GPS in most cell phones are not like those in your handy GPS receiver that you take hiking. Most cell phones do not allow the user direct access to the GPS data, accurate location determination requires the assistance of the wireless network, and the GPS data is transmitted only if a 911 emergency call is made.”
That’s the theory, in any case. But as we know from recent news stories, in fact
“…both the iPhone and 3G iPads [have been] storing a persistent list of locations and timestamps, and have been doing so since iOS 4′s release. While that’s mysterious and somewhat spooky in and of itself, it gets a bit stranger: the “consolidated.db” file is synced (in plaintext) as part of your iPhone backup, which means that it’s chillin’ on any machine you’ve synced your iPhone with recently. This data can then be taken and mapped to show where you’ve been and where you’ve gone since the last time you cleared everything off your device.”
Moreover, there are other “features” in some cell phones, of which users may or may not be aware, including “Geofencing,” which turns the GPS tracking on when the phone user has entered or exited a predefined region (like a school or office building) or crossed a virtual fence or border; “Speed alerts,” which provides an email or SMS alert when the phone has exceeded a speed limit; and “mobile to mobile tracking,” which may involve special installation of the kind of spy software mentioned in the previous post, or may be native to the phone itself.