An app that stops the user from wasting time on unnecessary stuff (idea from the movie "Click")

This app will only work when the phone is connected to Wi-Fi or any fast speed internet. The user can set the app to lock the phone for a while (say 15min) whenever they are doing unnecessary stuff (social media, watching videos, multitasking when they could focus on 1 thing, etc.) so that they can focus on their current work.