I have cited earlier that you have to be a MobileMe user or at least have to sign up if you want to use ‘Find My iPhone’ that comes with iPhone OS 3.0.

Here are the steps to enable the feature on the iPhone:

1. Go to Setting page on your iPhone

2. Select Mail, Contacts, Calendars and Enter your MobileMe web page

3. Once inside, there is an on/off switch for Find My iPhone, which you have to toggle on.

Once this is done you have to log into your MobileMe web page. After signing in, if you click on the accounts icon, you’ll see the Find My iPhone icon at the bottom of the account settings page. From here, you can choose either to find your iPhone on the map, send a message or remotely clear all stored data on the phone. 

Try it out. The feature turns out to be pretty neat one. However, I wish/pray that I never have the need to use this feature.