If you’ve had the need to use Find My iPhone to locate your iPhone, iPod touch, or iPad even a single time, you know the outstanding utility of this feature. Once limited to paying MobileMe customers, it’s now free for all iPhone 4, fourth-generation iPod touch, and iPad users, and will continue to be when Apple makes the transition over to iCloud. If you haven’t yet set it up on your device, here’s how to do so.
Open up the Settings app, then tap on Mail, Contacts, Calendars, and tap Add Account. Choose MobileMe, then use your Apple ID—it can be the same one you use for the iTunes Store, or a separate ID, if you have one—to sign up. Don’t worry if you’re not a MobileMe subscriber—logging in with a non-MobileMe ID will still give you access to the following screen, on which you can toggle the feature on and off. Turn it on, and you’ll be able to login on the web or from another iOS device using the same login and track, lock, remotely wipe, or just display a message or play a sound on your device.