This real life research project kills two birds with one stone: students will practice their research skills while working with you to decide on the rules for electronic devices in your classroom. It's a great activity for the start of semester, and in my experience, the students are much more likely to comply with rules they have helped develop themselves!
Cell phones in shoe organizer with student numbers. They are at the front of the classroom so all have clear view of their phone and can't say that someone "messed" with their phone. They are numbered to indicate which phone belongs to which student. I like this!