Apple's MobileMe offers a feature called Find My iPhone that allows you to track someone's Global Positioning System (GPS) on their iPhone. MobileMe is a paid service that bundles services including e-mail accounts, data storage, address book and calendar synchronisation, a photo application and the Find My iPhone feature. The iPhone features a built-in integrated GPS chip that works with the Find My iPhone feature to track an iPhone's location.
Tap the "Settings" icon on the iPhone and select "Mail, Contacts, Calendars." Tap the "Add Account" button and select "MobileME." Enter the MobileMe e-mail address and MobileMe password and press the blue "Continue" button. Wait while the iPhone communicates with the MobileMe server and sets up the MobileMe account on the iPhone.
Press the round button at the bottom of the iPhone's screen. Tap the "Settings" icon and select the "Mail, Contacts, Calendars" option. Select the MobileMe account and slide the switch located to the right of "Find My iPhone" to the "ON" position.
Open a Web browser on the computer and go to the MobileMe website. Enter the MobileMe user name and password and click the "Sign In" button.
Click the "Account" icon and select the "Find My iPhone" link. A map will open automatically that shows the current location of the iPhone.
Click the refresh button to track the iPhone's location over time.
Find My iPhone will only function if the iPhone is turned on. If the iPhone is off, the map will show the last known location of the iPhone.