I've never been a big supporter of rules (no matter how sensible they are) that are presented to students without discussion of why they are necessary. All of our classroom rules should be somehow tied to learning, and I believe it helps the enforcement of these rules if we can explain to students why the rules are what they are. To this end, Maryellen Weimer provides a very helpful summary of five studies that underscore the point that students can't both learn and do something else. If they're doing something else, they're not learning. Period.
In an experiment involving 62 undergraduate students taking a principles of accounting course, half of the cohort was allowed to text during a lecture and half had their phones turned off. After the lecture both groups took the same quiz and the students who did not text scored significantly higher on the quiz.I don't think that we need to jump to a no-technology-allowed-rule in our classrooms. Laptops, iPads, and smart phones can be useful to students as they problem solve or research answers. A conversation with students, on the other hand, about their proper use of technology in the classroom can be all the more convincing with these study results in hand.