Nintendo announced more details on the 3DS circle pad expansion during yesterday's 3DS event, including titles that will utilize it.
The new circle pad will be about the same size as the 3DS original, unlike the smaller one in famitsu's leaked image. In addition, the unit adds a new shoulder button to the right side - where it would cover the exsisting button, and new triggers to both sides.
Games currently confirmed to support the slide pad include Monster Hunter 3 G, Resident Evil Revelations, Metal Gear Solid Snake Eater 3D, Ace Combat 3D Cross Rumble, Shin Sangoku Musou VS, and Kingdom Hearts 3D.
A second circle pad is ideal for first person shooters and changing the camera angle in third person titles.
The unit will cost 1,500 yen (NZD$24.00), so if it isn't region locked importing could cost around $35 (including postage).