Here are a couple of accessory I'm sure you know all about. Never released but much hype surrounded them.
Made by Imega Corp, the makes of the Zip Disc format, this Zip drive was made to increase the Dreamcast's storage capacity but mainly for emails, web pages and other internet based files.
The 100 Mega-Byte storage disk drive is essentially the same as the ones made for PC's with slight modifications made to make it compatible with the DC. "We have chose a Zip drive for its durability and low cost. For gaming purposes durability is essential." said a Sega spokesperson.
The drive was conceived after their was a strong demand for more storage space than Sega servers were offering to save email and web pages onto. The Drive could also save game-updata data so all those extra quake maps could be played at home.
The drive was made to fit under the DC and would connect to the expansion port with the modem then being plugged into the Zip drive. This was help promote the DC from a console to a home entertainment / information system with the release of other accessory (Which were also never released).
This Zip drive was not going to be combatible with the PC Zip drives but it was suggested that software for the PC would eventually be released to make it compatible with the DC Zip drive.
The Zip dive was the have a retail price of $199US and be released some time in the third quarter of 2000.
I think everyone knows about this, the famous DVD drive displayed in 2000 but never showed working. Sega always said it would offer a DVD solution for the DC but it was obviously never released.
Some believe this never worked when it was shown and that it was an empty shell that was made to see if it could start enough interest to keep the DC battling with the PS2 as many believed that lack of DVD capability was the DC's only downfall.
Not sure how the DVD player was supposed to work with the DC, it does not look like their is a grove for the DC to sit on top of it. Maybe it was never made to connect to the DC and was only meant to be a separate DVD player for the home. If it did connect to the DC the guess would be that it would connect through the expansion port as this would be the only port fast enough to handle the information the DVD player would send.
The MP3 player is essentially a large VMU as you can see. It looks like it would connect to the DC through a controller port and you could download songs form the internet. It was never mentioned if this could connect to PC for downloading music but one would assume it would.
No specific technical information was ever released, only that it would be high capacity, connect to the DC (didn't see that one coming) and come with a pair of headphones. It was assumed that it would come in different colours but this was never confirmed or denied by Sega.