Taken from lik-sang.com
Check out
http://www.dreamcast-scene.com/ for the scoop also, I guess there is still money to be made with the dreamcast.
The DC/GP32 link cable works just like the GameCube / GameBoy Advance or Dreamcast / NeoGeo Pocket link cable does. If used with the right games, it will allow unlocking goodies, hidden features and whatever the game creators are coming up with.
The cable will also allow transferring saved games or MP3 files between the two systems. Just insert your MP3 CD into the Dreamcast and transfer your MP3 files straight to your SmartMedia card. Additionally, the creators of the KallistiOS Dreamcast development kit, Cryptic Allusion, announced that they're going to include support into their development tool.
The first game that will make use of the cable is the title Gianas Return, a game based on the famous The Great Giana Sisters by Armin Gessert, Manfred Trenz and Chris Huelsbeck (now at Factor5).