Nintendo has finally confirmed the "2nd analog stick" attachment. As seen in the picture, this attachment adds a fair bit of bulk, but also includes a second circle pad for a variety of games including Monster Hunter Tri G, Resident Evil: Revelations, Metal Gear Solid - Snake Eater, Ace Combat, Kingdom Hearts 3D and Dynasty Warriors VS. The price currently set is ¥1500 which is approximately $19.50 USD (direct conversion, likely to be lower). It requires its own separate battery source in the form of an AAA battery.
Needless to say this device has already received overwhelming negative criticism from the various leaks prior to this announcement. It adds a fair bit of bulk, renders the ABXY buttons too far to reach and also looks like a hunk of junk. To further worsen the problem, the device doesn't increase battery life as some had speculated. It's odd and I really can't see this being a success nor mandatory, so I am hoping this is just one odd, fairly isolated accessory for some die hard 3DS users.