easyvote is a web-based voting app that I wrote a couple of years ago. There’s also an Android app to go with it. My reasons when I started were 1) that it was obviously a useful thing to have the ability to do — to turn a class’ phones, ipods, ipads, laptops, PCs, etc into a cheap and ready-to-go voting system; and 2) the apps already out there were really clunky and hard to use.
Since then, neither of those two things have changed, but I do note that there are a lot of apps out there that now do this, some of them very slick indeed. However, I still maintain that mine is the easiest to use — for pupils and teachers. 🙂 More crucially, however, it is not platform specific, meaning that it will work on anything with a web browser.