When you purchase your 3DS it will come with six cards that you can use for variety of augmented reality software. One problem though, these cards are tiny. Want a life sized Mii standing beside you? Can’t do it with that tiny card!
Nintendo understands your need for life sized Miis though, as they have announced that they will be offering massive AR cards to Club Nintendo members in Japan. Details on how to get them have yet to be announced or if they will be available in North America or Europe.
Of course, you can always just print out your own massive 3DS AR cards, as many people are already doing across the internet, but that takes effort.