VMU MP3 Player
From Sega Retro
The VMU MP3 Player was a planned peripheral for the Sega Dreamcast first revealed at the 2000 Tokyo Game Show. The player would hook up to the controller port, much like the Visual Memory Unit, and would have a headphone jack on its left side. It was planned to have a 64MB disk capacity. The expected price of the MP3 player would have been under $100 USD.
According to IGN DC, Sega had been working on a strategic relationship with online music store MP3.com.