Nintendo, perhaps because of the stunning success with Dragon Quest IX, built a chance communication feature into the Nintendo 3DS where the system automatically exchanges data while passing other players in real life. This will probably be called Crosspass mode in English since Nintendo filed a trademark for that term a few months ago.
The Nintendo 3DS also has a Mii system and you can use pictures taken with the camera to make a Mii. This is part of a feature called “Mii Studio”. It’s also possible to transfer Miis using QR codes, a type of barcode that is popular in Japan.