Saw this on the Assembler games forum - wanted to post it here!

Dreamcast VMU Visual Memory MP3 (Unreleased) - YouTube

I've watched that video a few times and something I find odd is that the vmu mp3 player plugs into the Dreamcast via a controller type lead! (not through the controller as you'd think like a normal vmu)! (So realistically it's not a vmu at all)

Also you can see the 'beat time' adaptor thing (the big round disc thing plugged into the Dreamcast pad at 10 seconds into the video!!
I honestly don't think this is fake - I'm going to try to get in touch with the uploader.