Maybe have a practice that you can specificly practice spelling on ipod app? I have a friend who keeps spelling the same words wrong and I think this would be a good idea just to try help people memorise the spelling of extra long words as well.
I, too, would like a direct spelling practice. I don't code, so I have no idea how difficult it would be for Duolingo to highlight words I spell wrong and make me a spelling list, so to speak. I'm working on Spanish adverbs right now and all the words that are similar to English words, but just enough different . . . AGG! :-)