The Find my iPhone service is a great innovation of telephony which is available with the new IOS 4.2.1. Locate my iPhone is a free service that is available only for iPhone 4, iPod 4g and iPad users. iPhone 3G and 3Gs can also use this free service, but only if you follow a few simple steps. Firstly, you need access to someone's iPhone 4 to create a MobileMe account . Then, the account information has to be entered in the iPhone 3G and 3Gs. Now enable the service option, and your iDevice will be able to avail the find my iPhone free service.
Activate 'Find My iPhone' on iPhone 3G and iPhone 3Gs
The big surprise that accompanied the IOS update 4.2.1 was the free 'Locate my iPhone' (Find My iPhone) service. Unfortunately it is free only for iPhone 4, iPod 4G, and iPad users. However there is a trick to get the free service on your iPhone 3G and iPhone 3Gs. The only requirement is you need to know someone who has an iPhone 4. Here's how to do it:
Bring an iPhone 4 and create a MobileMe account. A mini guide is available by following this link (use the iTunes account that is linked to your iPhone 3GS/3G)
Take your iPhone 3G/3GS and enter the MobileMe account information that you created for the iPhone 4. The option "Enable the service" will be available. The MobileMe account on the iPhone 4 will disappear automatically. Do not forget to download the application on your device