I-Phone Application

we are interested in developing an iphone appiocation about sending sms. we want the apilcation to have a natural feeling of the phone and the default sms application of iphone (just as viber and whatsup does). what the application will do is to let the user install it for free to their mobile phones and send individual or bulk sms to their friends. there must be options like send to all, or even the user will be able to select one by one the users he wants to send the sms to. also he will be available to check delivery reports, and his account balance. he will be able to buy sms credits, he will pay via paypal ONLY. me as an admin must have full access and administration via a website that we will do. i need to add/edit/delete new users, transations, sent sms (the server sms id of them NOT THE CONTENT OF THEM), and also the delivery reports status of each (grouped by username or date). i already have 2 http apis. you will insert both in the application, and via the admin panel i will have which one will be activated, and i also will be able to change between those 2 whenever i want. please also provide me more ideas or proposals about this project, we are fully open.