ADSB Flight Tracker Lite is an app that allows you to track planes in the local area and worldwide using a radar style similar to the radar screens that Heathrow air traffic controllers use in the real world. The app has a map view as well as a list view and allows you to track planes in your area as well as worldwide. It can be downloaded for free and works on Android devices. It is designed to work in the background and does not require any additional hardware or software.