Nintendo 3DS System Update v. 4.0.0-7 adds a QR Code option — the 3DS has been able to scan QR codes for ever, but now the eShop gives you a new option. Tap this in the Settings/Other menu, scan a QR code and it’ll open the relevant page in the eShop.
The QR Code function in the eShop is also an alternative to Download Codes. You’ll be able to Scan a QRcode in order to Redeem Gifts like Games, Apps, and Cash Credit. Basically so you can easily purchase content online and then send it to your 3DS. Nintendo has said that they’re working on an eShop Website, and also it would make redeeming Club Nintendo Prizes a whole lot easier.