Some suggestions for "more gamification"
Hello, I'm a PhD student at EPFL and have done some studies on gamification and human computation. My question/idea is about translation part. Why don't you make the translation task kind of game/race. For example the same sentence may be given to two persons so that they translate it and compare based on other translations of that sentence. One other idea would be to include sentences of the web during the learning phase, provided that the user has already seen all (or all but one) individual words of that sentence. I have some other minor ideas, if you are interested.
I think this human computation is a very interesting topic and will become more and more significant in the future.
I love the idea of incorporating the to be translated sentences off the web, in the lessons, I didn't know how they would do it, but what you say is true so long as the English words we have already been taught to translate are in there we can translate it. An they can do what they do with reCaptcha, compare with 10 or so other translations, if its the same, done deal.