From Sega Retro
The Dreamcast Microphone is a microphone peripheral for the Sega Dreamcast. Taking up a VMU slot, the microphone was developed for use with Seaman, though was also compatible with Alien Front Online and Planet Ring. Had Propeller Arena been released, this too would also have been compatible with the accessory.
Though not a particularly successful peripheral, it was one of the first microphone peripherals for video game consoles and would inevitably inspire later peripherals for the Xbox 360 and PlayStation 3.