This might be the closest thing: http://bots.duolingo.com/ http://bots.duolingo.com/ If they had an API (which, they do not), somebody could build a TTS + voi

This might be the closest thing: http://bots.duolingo.com/ http://bots.duolingo.com/ If they had an API (which, they do not), somebody could build a TTS + voice recognition wrapper for this functionality, creating the experience you mentioned.