Classroom response systems (commonly known as 'clickers') are an important tool that can be utilized by faculty to promote student engagement in class. At Auburn a wide variety of classes are using clickers - Biology, Chemistry, Physics, Political Science, Forestry, Spanish, Pharmacy - to name a few. At present, there is no consensus with respect to brand or vendor amongst the different users on campus. The Biggio Center can loan you a set of clickers for classes up to 30-40 in size. This would be a good way to try them out in your class. The Instructional Media Group maintains a page on clickers. Also, see Vanderbilt's bibliography.
Faculty are using clickers in many ways: "...for promoting interactivity, gathering feedback, preassessing knowledge, and assessing students’ understanding of lecture concepts", "...trolling for misconceptions" etc.
From the Carl Wieman Science Education Initiative Clicker Guide: "Clickers are not a magic bullet – they are not necessarily useful as an end in themselves. Clickers become useful when you have a clear idea as to what you want to achieve with them, and the questions are designed to improve student engagement and instructor-student interaction."