Just discovered another interesting site (this one DOES work in the UK though) for creating quizzes that students can download on their phones. I created one today and I've sent an SMS to my students with the details to access it on their phones. You can see the very short example I made here. I've asked my students to try it out and see if they can a) download it and b) do it. There's no fee involved, except the cost of sending an SMS to my students to tell them about it. The only downside here is that the students must be able to connect to the internet on their phone to download it, something that they may not want to do for financial reasons or be able to do because of the type of phone they've got.
I've asked my students to try it out and to give feedback on it, so I'll report back once I've heard from them.