This could be a godsend of a device, especially for shooter and RTS fans, as the revered mouse/keyboard combo is noticeably more accurate than control pads. Microsoft has gone out of its way to not support these devices on the 360, claiming they would make the playing field uneven. We think it's more likely that MS doesn't want to lose players from the PC gaming market, where MS has a vested interest with its Windows platform.
The original Xbox had a similar gadget in the Smart JoyFrag. This allowed full mouse/keyboard support in Halo 2, giving JoyFrag equipped players a definite edge over their competitors. We've contacted the makers of the device so we can try it out - we'll tell you all about it if and when it arrives.