Can you locate an iPhone with the iPhone having an app?
Yes, you can find your lost iPhone with an iPhone app. However,
you must have access to another apple product with the same app to
locate your lost iPhone. It's called FindmyiPhone in the app store,
and it's free. All you do is make an account. Let's say your iPhone
is lost, all you do is sign in with your account with another
device with the same app and the app will do the rest. Its quite
amazing.