I declare this month to be SeMP3mber with all of the MP3 news that we have lately. I got some more information from InnoGear about accessories for the MiniJam, and while I'm waiting for pictures before posting the list, I can say that the list (12 items!) is quite impressive.
Yes there will be a battery pack for the MiniJam, as well as a cassette adapter and flat panel speakers (yes!). Additional cases will be available at some point as well.
The MiniJam does not work with serial cradles, and I'm waiting confirmation on Windows 95.