Are there any tools on the market that employ prosodic research to help overcome speech impediments?

There is some software available. For instance, the Get Rid of Your Accent app and the many Speech Therapy Apps.

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.