MP3 Flash Module as External HD Interface?

otter42 asks: "Has anyone thought about using a portable MP3 player's flash module port to interface with an external hard drive? I think the major obstacles are: how to find the protocols and write the interface, how to build a interface port to IDE card, and how to power the external drive. Having a 10 GB HD for $100 sure beats the heck out of 32 MB for $90! I'd be willing to pay an extra $100 so that my Rio could carry a worthwile amount of music." I'm sure someone has looked into something like this...if so, please share your experiences!