iCloud: Find My iPhone overview
You can use Find My iPhone to:
See the locations of your devices on a map
Lock and track the location of your iOS 6 device using Lost Mode
Lock your iOS 5 device or Mac computer
Make your device play a sound
Erase the information on your device
Access Find My iPhone from a computer
If you’re already using another application on icloud.com, click the iCloud button (or press Shift-Esc on your keyboard), then click Find My iPhone.
To get started, set up your devices now.