Pictures of the device first appeared in Famitsu, which explained that the add-on would add a second analog joystick and extra set of shoulder buttons and would be bundled with Monster Hunter Tri G. It will also include a black wrist strap similar to the Wii. The first game to support it was Monster Hunter Tri G in Japan and Resident Evil: Revelations in Europe and North America. Other titles announced to be compatible with the slide pad are Ace Combat 3D (Japan version only), Metal Gear Solid: Snake Eater 3D, Kid Icarus: Uprising, Kingdom Hearts 3D: Dream Drop Distance and Dynasty Warriors VS.

Source: Wikipedia, "Nintendo 3DS", available under the CC-BY-SA License.