Awesome advice! It just so happens for my start-up we're working on language learing apps, and our first one is for Mandarin Chinese. Here's our first one in the itunes store (it's free!), would be great to get some feedback, as a single founder it's been tough to get constructive criticism.

iTunes apps page: http://itunes.apple.com/us/artist/321speak/id382201422 our site: http://321speak.com