This chapter describes a new class of audience response systems: an instructor mobile audience response system, or IMARS. While the typical ARS features mobile data entry devices in the hands of students and a desktop console for the instructor, the IMARS features a mobile device for the instructor and almost any device with a browser for students. The ClassInHand™ software, developed at Wake Forest University, is an example of a prototype IMARS system. It has the principal benefit that the system frees the instructor from being tethered to a desk during class, by turning a wirelessly connected PocketPC into a mobile teacher console. This chapter describes the basic components of an IMARS system, and discusses how it has been used in an educational setting.