"I know you are busy adults with responsibilities outside of this class. Communication is important, and this class is in part about how to be better communicators. Sometimes during class you may get a call or a message from someone that you must answer. I understand, and I promise you that if a family member calls or messages me, I will answer it. Then I will answer to you. I expect the same consideration. If you use your cell phone in class as a communication tool, by that I mean not as a tool for learning English (bilingual dictionary, recording your English production), then you will send me a 200 character explanation of how you like to learn English. It is due within twenty-four hours after class, and is worth one quiz grade."
My plan now is to keep my policy. It works pretty well, but is rather intimidating to some students. In fact after receiving a message from a student last semester, he dropped the class. I wonder what students focus on during class. Most of the time when we interact with each other, they seem to sincerely enjoy themselves, but their attention often drifts to the cell phone, their scheduler, another student. I found two interesting videos on the subject by Howard Rheingold, Attention 101 and Attention 102. Very few of my students carry laptops to school, and I have never had a student open one during class. That is probably the nature of Japanese universities, or at least this one. At least I don't have that to compete with yet, but there is plenty else.
Competition is a good thing, and I try to remind myself that part of the reason that students may not be engaged in class is that my class might not capture their attention at that time. A little motivation for me to keep it interesting and pertinent.