Startup Idea : phone oyster card

instead of us using a plastic smart card 'Oystercard' we could just use our phone as most of the time we forget our oyster card... this app will be registered with London transport as they do oyster cards. this app is for London Underground (the tube), London Overground, buses, night buses, the Docklands Light Railway, trams, and National Rail. (LONDON) while going on the bus you can scan your phone app and this app will also will remind you when you need to top up next and what your current balance is and more...