there are so many shareware and freeware that does exactly this. There is really no market for something that there is already so much freeware and open source for.

There are programs such as Free Audio Converter from DVDVideoSoft.com things like http://www.mediaconverter.org/ that you don't even have to download, that the idea of this product is about 10 years ago. I think that it may work if you add it to a suite where you can convert video and download video, but as it sits right now it is only good as a freeware or an Open Source.