So it's real, then: the Expansion Slide Pad, which equips the Nintendo 3DS with a second Circle Pad, actually exists. It'll launch in Japan on December 10 and cost 1,500 yen (about $20). It'll require one AAA battery to operate, putting to rest the rumors that the device might also include an additional battery for the 3DS system itself.
Nintendo's also announced the titles which will support the Slide Pad. These include Monster Hunter 3 (tri) G, Resident Evil: Revelations, Metal Gear Solid Snake Eater 3D, Ace Combat 3D, Dynasty Warriors VS and Kingdom Hearts 3D [Dream Drop Distance]. Notably, these are all third-party titles. It isn't yet known if these games will require or simply support the Slide Pad as an optional extra. Those titles which do use the device will sport the icon seen to the right on their packaging, however.
There's no official word on the Slide Pad coming to North America and Europe as yet, but the supported games certainly are.