Cycle Gym iphone app and backend

wanter an iphone app for a busy cycling gym where people can logon to there account and view how many pre paid sessions they have left and also reserve the exact bikefor a session. the app will need to be able to keep track of sessions avaiable at the gym and also if there are any bike left to reserve for a session. customers will buy credit at the gym where staff will add it to there account from there each time a reservation is made credit is taken from the account. would also like a way for calander sync for the session time and avg calories burnt. all the backend and accounts for users will also need to be set up