"Some of this only recently became technically possible. The new ScreenTime API from Apple allows users to connect apps on their phone to third party apps (like us). We receive opaque "tokens" for each user app selection and we can perform actions on the tokens, which affects the apps without us knowing what the actual apps are. We can add and remove "shields" to a token, which presents an obstructing interface over an app or website. We can display a user's usage of a token over a time period and display that data to them."