Will require a single AAA battery to power it
The Nintendo Sidepad accessory for the 3DS is now confirmed to arrive in Japan on December 10th, according to the company during its pre-Tokyo Game Show press conference. The second controller accessory will require a single AAA battery to power it and it will cost about $20.
A number of titles that will take advantage of the Sidepad on the 3DS include Monster Hunter Tri G, Resident Evil: Revelations, Metal Gear Solid: Snake Eater 3D, Ace Combat 3D, Cross Rumble, Dynasty Warriors VS, and Kingdom Hearts 3D: Dream Drop Distance. More titles offering Sidepad support are apparently planned, but have yet to be announced.
No word from Nintendo on when those outside of Japan will be able to get their hands on the Sidepad, but at this point early 2012 is a safe bet, we think. In addition to the Sidepad, Nintendo confirmed a pink colored version of the 3DS that will arrive in Japan on October 20th and there was no word on if or when it would be offered outside of Japan.