Access the App available in the App Store. Whenever your phone and this key finder go out of range with respect to each other, both the phone and device will make a sound alert. And the tracker can also provide a last seen pin-drop position on the map for better tracking of your items. Attach your key-finder to any of your items such as a wallet, pet, child, or car, and the tracker helps you recover your items. The battery is contained.1.37" W x 5.11" H