I see a lot of language learning software, apps, intelligent games on the market, but nearly all of them focuses on grammar and lexical aspects of linguistics. I wonder if any techniques are dedicated to prosodic aspects of language acquisition, to helping learnings lose their accent or children overcome speech impediments.
When it comes to speech therapy dealing with impediments, this is often so highly individualised that it almost always requires a trained person to intervene. That is not to say that some computer-assisted solutions would not be possible or useful but any software solution will only be a small part of the intervention.
Also if you look at the kind of work it takes to achieve prosodic proficiency - particularly when it comes to accent removal, you can see that software can only take you so far. I recommend looking at Melody Noll's Ameritalk for some examples: http://www.ameri-talk.com.