I’ve been curious about some of the services that can track the location of your GSM phone using GPS. Are any of these available in the US for Cingular customers? Are any free?
The short answer is not for Cingular, but it may be possible in the future. It probably won’t ever be free.
First, realize that phones do not have a full GPS receiver. Much of the computation needed to locate someone must be done by servers in the operator’s network. The location then is usually overlaid on a map to give the user something useful. It would be hard for a third party to provide this service.
I know Sprint offers a locating service and they do charge for it. (Also note that they send a text message to the phone being located letting the owner know their location has been sent.) I imagine Cingular will introduce a similar service in the near future. If history is any guide, Verizon will follow in a year or two.
Actually special WAP sites are able to request your position from the towers somehow. If you have programming skill you can check Cingular’s development boards to see how this is done. It might be possible for you to make your own WAP site that simply displays your location on a map or something like that.