Phone app to prevent students from using their phone during lesson

Hello everyone. I am a post graduate student studying computer science. I am required to write a dissertation which requires me to implement a program. I have decided to write an android app to prevent students from using the phone during lessons (if the teacher allows it). The app works by the teacher creating a group that the students can join and if they leave the group for more than a minute while a session is ongoing, it will be recorded. Any suggestions on how it should work will be great.