Startup Idea : Busy (Title Undetermined)

I want to solve the problem when you try to call someone or text someone, But you don't know if they are available or if they are busy. I want to make an app that allows you to set time frames when the person you intend to call is either asleep, at work, or otherwise busy. So you can know when it is appropriate to call friends. You can set time frames yourself, or, the person you intend to be calling or texting can set time frames where they think they are busy. So, When you try to call someone during these time frames, It will give you a custom notification that says something like, This person is currently asleep, Are you sure you want to call them?.