Hey Aaron,
I've recently signed up for a Digital Locker at
mp3tunes.com. At work we run Windows 2000/XP and since I also own an iPod I use iTunes. My library is quite extensive so I purchased my locker for several reasons... but mostly because that my entire library stays synced with my external "locker". At any rate, one of the features you get with a locker is streaming support through a Web Interface, through iTunes "shares", and there is now an SDK as well.
My goal is to create a Banshee plugin that will connect to my Digital Locker, retrieve my library contents, and stream playback through Banshee (like iTunes already does). Now, I'm not sure just how far I can really go with this. I've got years of development experience under my belt... but that's under Windows and quite honestly, I've found the development learning curve on Linux to be rather difficult. I had hoped monodevelop might be the answer to that so I was rather excited to see that banshee svn included a monodevelop project/solution file. I'm still going to give it my best shot but we'll just have to see how it turns out. The actual SDK itself is quite simple to use so this should be pretty easy to realize if I understand all the underpinnings correctly. I have another goal of creating a Tivo HME application to do the same.
Matt Philmon