There are a ton of calendar, reminders, and notes apps out there. For some reason all these developers don’t integrate Contacts. The reason this is important is that the world revolves around People. You make notes about your interactions with People, you have appointments with People, You’re reminded about tasks that are related to things about People. Someone may say “well I don’t work with people, and I say, all tasks, activities, appointments, and notes you make in some way deal with people, even if it’s just yourself (pretty lonely by the way).
Please consider integrating People.