Nintendo mentioned a browser-based means for Wii U and 3DS users to make eShop purchases some time ago, and although nothing has been officially announced, it seems that inquisitive NeoGAF members have stumbled upon what could be the start of just that with

Though the site is fairly simple right now, it actually does work for redeeming download codes (in certain regions only). On the eShop page, you’ll see a button directing you to a code-entry screen. After logging in with your NNID you can enter a 16-character download code to begin downloading the game automatically on the appropriate device.

Check out the screenshot below for some proof of the site’s existence. Some regions (Australia for one) will not get further than the code entry button, instead seeing a lovely “This website is currently unavailable in your region” message. Let us know if you’ve had any luck with the mystery site!