Two years ago fellow blogger Frank Franz turned me onto Polleverywhere.com where students can answer multiple choice questions using their phones. For those who do are not allowed to have their students text, they can use gopollgo.com. The teacher would send out a Tweet and the students would then answer and you can get an instant poll. This is the perfect way to create an "exit ticket" and have the kids answer several multiple choice answers and show you and the entire class (if you are showing it with a LCD) the percentage that got each question. Above is a video explaining it as well as giving a little history how a company begins.