I've been looking at various options for student response systems - primarily clickers - and have been quite frustrated at how that market is set up. I wouldn't be able to recommend use of those, in good conscience, given the recurring costs. It also seems a little strange to compel students to buy a specific piece of hardware to perform the task, when they (almost) all have laptops and/or smartphones in their hands anyway.
Why not just use a browser-based polling system to solicit and collect student responses during class? Ideally, it should be easy for the prof/instructor/TA/teacher to add new questions on the fly, which appears to be a weakness in the current web-based polling systems. But it feels like a much more productive approach, rather than sinking money into vendor-locked hardware that students have to pay to unlock each semester.
This isn't the first time I've looked at web based systems to handle student responses and feedback. Last summer I was looking for something to fit the bill, and didn't find anything that really did what is needed - a simple, frictionless, flexible app that lets profs (or anyone else) ask a question (or a series of questions) and gather responses in realtime, and also allow on-the-fly modification and posting of new questions.
It seems to me that something like PollDaddy, TooFast or PollEverywhere (which allows response via SMS and the web) may be more appropriate, but even these aren't quite what's needed.
[polldaddy poll=1364276]