Hi,
I have experience working on a similar project.
Briefly, I create app which consist of call recorder and sim manager sections. Call recorder has to option: background recording and manual when you can select the call you want to record. Sim manager allow to disable sim card for specific numbers.
If you are interested in it I can create similar features for your project.
Unfortunately, Android OS doesn`t allow to implement these features:
4. Don't show in task manager. (Running APP)
5. User can't uninstall the app.