Sega's Visual Memory Unit aka "VMU" was released in the year of '98 along with the initial release of the Dreamcast.
This was one hell of a memory card. It was revolutionary in many ways. Not only could it store save files, but it also has a screen that'll allow information and junk to be displayed.
Here are some of it's uses. The main use is, storing save games. Every Dreamcast game worth mentioning has VMU support. I've never heard of one that doesn't. The games do anything from just displaying a simple logo, to uploading a full minigame that you can play anytime like a gameboy (Sonic Adventure Chao Adventure for example).
Also, you can link 2 VMUs and transfer data, even link up and fight on certain games.
Here is an image of the VMU:
Pretty neat little gadget, isn't it?
Anyway, you might be wondering, "How the hell does that work with the game?" I'll show you. Here is another image:
The VMU slides into the controller and displays stuff while you play. I freaking LOVE the VMU.
In the case of our game, the VMU will display all sorts of stuff. During main gameplay, you'll have a choice whether to display life, ammo, frags, and other crap on the TV, VMU, or both. When you die, it'll show a kick ass image (courtesy of Dark Crusader). The VMU will do all sorts of stuff for our game. The artists are designing VMU graphics.
Any other questions or comments? Ask here.