There an app called find your iPhone. It's free if what your looking for is another apple device.
I agree with Gina -- use the Find my iPhone app that is free. Enable it on the iPhone. Then, you can login to icloud.com on a computer and locate the phone. It is very accurate -- within a few feet most of the time. Plus, if you lose your phone (in your house, car, etc.), you can use Find my iPhone to play a sound -- even if the phone is on silent or vibrate only.