I have heard that some teachers have a basket at the front of the room where they collect their students' cellphones before the start of the class. I think this could be helpful however, there are now smart watches and other wearable technologies that can provide the student with access to the Internet. So I feel like this does not tackle the entire problem and that more needs to be done in the classroom, such as addressing some of the underlying factors that put students at risk (which may include parental/family factors as you mentioned Beth) and teaching practical skills for safe Internet use as you mentioned Lisa.