Some newer phones have a built-in GPS capability. They have a GPS antenna and the software to acquire a pretty accurate Lat/Long. You have to turn on the GPS in your smart phone's "Settings" or "Preferences", by default it is usually turned off.

Most smart phones need a network connection to download a map to show you, in a graphical format, exactly where you are.

It's odd that you bring this up today though, because I just wrote the code to grab that data from a GPS enabled smart phone last night. I'll probably add a feature that will place your location on a map tonight sometime.

In the meantime, if you have a smart phone with a GPS, and you want to test its accuracy, you should be able to get your lat/long from it here:

http://navigraphic.com/locate.html