Here's how it works. Download and install the app on your phone. Also, make sure the "iCloud" option is fully activated as well as the location services in the phone's settings. Now the iPhone is registered and ready should you need to find it.
When the phone goes missing, simply log into www.icloud.com from any computer. Enter the same log in information as you use on the phone. The website will locate the phone's signal within seconds, and show you the location via GPS tracking on Google maps.
You then have the option to send a message alert to the phone; kindly informing anyone with the device that you know where they are located.
For those who rely on their iPhones for everything from email to directions, texting to games, installing this free app seems like the right choice.