Build iPhone app

I want an app built to be downloaded from the App Store. The main purpose of the app is to record and save phone calls and voice msg's to the iPhone. My initial research indicates that it's not possible to integrate the app itself into the native calling function programmed into the iPhone. Instead, the app would need to run as a 3rd party. Effectively meaning that the app would need to be opened, then the recording screen locked to the top of the screen above the iPhone calling menu when a call is made; thus allowing for the user to select either 'record' or 'stop' from the main iPhone screen without having to switch between apps/screens. I desire the app to be very simple to use and to look as similar as possible to the native iPhone calling screen - thus to allow for a great perceived sense of integration. Within the app itself, I want two tabs at the top or bottom to switch between two screens; the recording screen and where the files are saved to. When the files are saved, I want the option to be able to name the file (as well as the date and time the msg was left), set a reminder (to call back or some other action) and also to email or MSG the recording. Please request any other info that may be required in helping to build the app.