Here is an update on the second joystick add-on that is coming out for the 3DS.
Joystiq reports that the add-on will be coming out on Dec 10th of this year in Japan for ¥1500 or roughly $19.50 and its currently called "The Slidepad". It looks to be final too, there maybe some design changes between now and then but that's a maybe. All that is known for sure is that it is coming out this year..... in Japan. It also looks like it will not be some kind of battery life extender because it need a single AAA battery for it work.
The Monster Hunter update is that there are 2 Monster hunter games coming out for the 3DS. Monster Hunter Tri-G (an update of the Wii Monster Hunter Tri) and the New Monster Hunter 4. Both in 3D and it is comfirmed that Tri-G will work with the SlidePad and a list of a few other games those being: Biohazard Revelations (Resident Evil: Revelations everywhere outside of Japan), Metal Gear Solid : Snake Eater 3D, Ace Combat 3D: Cross Rumble, Dynasty Warriors VS, and Kingdom Hearts 3D: Dream Drop Distance(see what they did there in the title). Monster Hunter Tri-G will come out at the same time of the "Slidepad" in Japan so its easy to assume that Nintendo will bundle the "SlidePad" with not just the a system but with Monster Hunter Tri-G. In case you dont know why this is a big deal, Monster Hunter is like Digital Crack in Japan, millions are hooked and this is one of the best ways I can see Nintendo selling millions of units over there, I can even see there being a special edition 3DS color system with graphics on it.
Lastly here is the trailer for Monster Hunter 4 and thats on the 3DS were looking at.
Joystic: "SlidePad" Release date and price