There are a number of products that act as personal response systems (also known as student response systems or “clickers”) that work with the iPod Touch or iPhone. Here’s what I have discovered so far:
Turning Technologies ResponseWare is versatile but there is a subscription fee that each student must pay. Also, the system pings Turning Technologies server once each second so you have to make sure your network will be able to handle that amount of traffic.
The eClicker by Big Nerd Ranch is limited to 32 clients (students). The Host application (for the instructor) costs $24.99 but the client app is free. The system is WiFi-based so an Internet connection is not necessary since the teacher can set up a wireless network (easily) if he or she has a Mac. (I don’t know if it is easy to set up a wireless network with a Windows computer.)
The app that seems the best (from what I can see) is iResponse Classroom Responder System. The app for the clients costs 99 cents and the host for the instructor’s computer is free. There is a Mac and PC version and there is a basic and Pro version for both platforms. The iResponse system is also WiFi based. Instructions for how to set up a wireless network with a Mac as well as instructions for using the software are available.