Cellphones?

I'm looking for advice from my PLN about cellphones in the classroom.  I know I've seen tweets making fun of schools that don't allow cellphones, etc.  I have activities that use cellphones in my classroom.  But I'm talking about the daily lessons and students having cellphones out and playing games on them or looking for music, etc.  Do you ever ask students to put away their cellphones?  Are your lessons so engaging that they are never tempted to play Clash of Clans while your activities are in progress?  I want to handle cellphones in the best way possible this year.  I teach freshmen and the cellphones aren't usually a problem until about January when they get comfortable/cocky and start using them all the time no matter what is going on in class.  Some have even asked me to be stricter about them so they won't be tempted.  I notice that they think they are great multi-taskers and it takes away from the group dynamics of even a fun group game when they say things like, "I was only looking at my phone while I was waiting for my turn."  Well, you could have been learning from the other students' turns and just being respectful and having fun attending to the game is my thought.

I plan on using phones on the first day of school with Kahoot! and signing up for my Facebook page and Remind.  I was considering having a discussion with the students about respectful use of cellphones and why you don't use them during a game or an activity, etc.  I don't know how to handle the cellphone issue, to be honest.  I want to be 21st Century, but I also want to do what's best for their learning and for my sanity.  I'm not interested in "punishing" them for their cellphones.  I want more creative solutions.  Please let me know how cellphones are handled in the progressive classroom!