UPDATE: Please take a look at the comments below before you decide whether or not to try iVoted.
This looks very similar to Poll Everywhere, but without any educational pricing or options, is it a viable alternative, or just a carbon copy? I do like the fact that you can use email to vote – and most students will have access to email in a computer lab or on a smart phone if they have that.
Poll Everywhere does provide a free account for K-12 educators and is, right now, the best system out there for you to at least TRY using Student Response Systems in your instruction. If it works well for you, then upgrade your account or look at trying to get a dedicated system to use for instant formative feedback in your class. SMART, Promethean and other interactive white board providers make available.
Now, if I can only find an alternative to TextMarks…