I heard I can find my iPhone if I lose it, or I can track it down if it's stolen. How does this work?

Apple recently announced it is now offering a free service for iPhone 4 (as well as the iPad and fourth-generation iPod touch) called Find My iPhone, which will help users locate missing devices. Previously a feature in the $99/year MobileMe service, Find My iPhone is now available at no charge to users who've upgraded to the latest iOS 4 software. Those using an iPhone 3G or 3GS will still need to subscribe to MobileMe in order to find their smartphones.

How does it work? If your iPhone 4 is lost or stolen, simply log into your password-protected account on Me.com -- or via the free Find My iPhone app installed on another iPhone, iPad or iPod touch -- and remotely set a four-digit passcode lock to prevent anyone from using your missing device.

Better yet, you can make the device ring loudly, even if it’s on mute, by typing a text message that will appear on the iPhone's screen (e.g., "Please call me if found: 212-555-0100"). So if, say, you left your phone under a pile of clothes, you’ll still be able to find it.

If you’re not sure whether your device is at home or your office, you can locate it on a map using the device's A-GPS (assisted global positioning service technology) radio, which uses cellular connectivity along with satellites that hover above the earth to find your phone. Note: Even if you can see where your phone is on a map, you need to contact the authorities to retrieve any stolen devices rather than trying to get them back from thieves yourself.

Be sure to take advantage of this free feature. But remember: You need to activate Find My iPhone before you lose it, so do it now. To get going, tap the Settings app on your iPhone, followed by the tab that says "Mail, Contacts, Calendars" and then "Add Account." Next, choose "MobileMe" and enter your iTunes or Apple ID and password (same as you would when buying media on iTunes). In the "Find My iPhone" option, slide the bar to "On" to activate the feature.