I think that duolingo is missing some conversational programs. Something were the computer is talking and it's up to the student to figure out how to respond back and make it were there is a conversation between the player and the computer.
Too complicated to implement. That's sci-fi. Though you can always speak with Siri in your target language I guess :P
If you're learning Spanish there's this program where you are supposed to be speaking with a doctor. It is not perfect but it is something xD http://dr-abuse.softonic.com/descargar#downloading
(Be careful if you download it, uncheck all the boxes)