My philosophy professor had an interesting policy. He told us that if a phone rang in his class, he would answer it in front of everyone. If he caught you texting he would stop in the middle of the lecture and tell you not to show up again if you'd rather be texting. Cellphone usage dropped by 99%. One time a phone rang, which he answered, and it turned out to be an actual emergency. He was fine about it and let the student take the call.
During Chem exams we were not allowed to bring ANYTHING aside from a calculator and pens. If you insisted on a bag, it had to be left at the door. If they even suspected you had a phone on you, you'd fail the exam automatically.