With iOS 4.2 Apple has made the Find My iPhone service free for everybody. Here is how to access the free Find My iPhone service.
Find My iPhone is a service provided by Apple that allows you to locate your iPhone, iPad, or iPod Touch via GPS on google maps. It also allows you to lock your phone or make it alarm so it can be found more easily. You can even completely wipe a lost or stolen device. With iOS 4.2 Apple now provides this service for free.
1. First, update your device to iOS 4.2 if you have not done so already
2. Click the Settings icon
3. Select Mail, Contacts, Calendars
4. Select Add Account
5. Select MobileMe
6. Input your Apple ID username and password (or create one if needed)
After the validation process, you may access the Find My iPhone/iPad interface at me.com