My t had her cell phone out once during session because her husband had just gotten out of the hospital and she wanted it out in case he had an emergency. She respectfully asked me ahead of time if that was ok. Other than that one time, she doesn't even have her phone out in sight.

Now my daughter's t has her cell phone out every session. She uses it for time, which is fine. However, she doesn't turn off the ringer. Sometimes she even answers the phone. It's a major pet peeve of mine so she tries to be somewhat cognizant of that. She's older and kind of forgetful I do need to remind her to knock it off periodically.