IOS Device Monitoring/ Activity Logging App

My client wants to track the activity on their apple device. Logging messages and screenshots of certain messaging apps. They do not want to deploy third party apps due to security issues that may arise. The app must conceal itself completely if possible or appear as something which suspected people will not notice. If you accept the job each development step must go together with me in my inspection so expect answering a ton of questions and writing comments in the code. I will not ask for any rights for this app. You write it it is your app. We are not trying to harm anyone. This is only for protection purposes. I do not have any IOS development knowledge. Although I know C, Java, JS and node and etc. So it may take you some time explaining me what API what framework what tool you use for what purpose as we develop the app together. If you have any questions feel free to ask.
I don't know much about the pricing for such an app since I mostly do web dev.