Tracking stolen iPhone – Find My iPhone from Apple
“Find My iPhone? app enables to locate stolen iPhone (iPad) or beloved members of family. The app from iTunes app store is free, but to use it you will need to sign up (purchase) for ?Mobile Me?. Apple offers 60-day free trial. After that USD 99 / year with 20 GB of online storage.
Related links: Apple, iTunes store, Mobile Me, Mobile Me Pricing, “Find My iPhone” at iTunes Store