"Hand it an MP3 URL plus start/stop times, and it hands you back the corresponding slice of the file."
Brilliant. Being able to link to a specific segment, specific points in time, will greatly enhance the hypermedia experience. Before reading your article I was thinking of a hypermedia timeline as part of the url. For example
will take you one minute and fifty eight seconds into the Real Media file called "test".
Looking forward to reading more on this topic:-)