Heya! Lurker/Newbie here. Can't believe how many regular posters are asking questions that are obvious. I've been in contact with someone who's known about this for a while now, and can assure you it's real. I can also assure you that it blows ass and won't be worth purchasing unless you're extremely desparate.
Here's a little FAQ for you.
*Is this real?
Short answer: Yes. This is a real product and will really allow you to play 3DS ROMS on your 3DS unit.
*How does this work?
It's a tiny bit more complicated than this, but I'm dumbing it down so that everyone can understand. Basically, this is a shell for an SD card slot which tricks the 3DS into thinking that the SD card is the game cart. By putting the ROM into the SD card, and the SD card into the shell, you've essentially created a 1:1 copy of a retail game; a bootleg.
*What does that mean for the user?
A couple things. The SD card has to be the correct size for the ROM. If you have a 2gb ROM you need a 2gb SD card, and so on. You cannot use a larger card than the ROM you're using, which also means that there's no way to store more than one ROM on the card at a time. Additionally, the save files are stored on the cart shell itself, as the spot for that is standardized. This means that if you change the ROM, the new game will see that information as a corrupted save and delete it. You'll need to back up your save files before switching ROMs, and you may need additional hardware to do so.
*Can it run homebrew?
Nope. This won't allow you to run unsigned code. The cart is set up in such a fashion that you've created a 1:1 copy of a retail cart. That is, it's signed by Nintendo already, and that's why you can run it.
*Can it get around region blocking?
Nope. For the same reason listed above, you'll still need to use the correct region's ROM for your hardware, and won't be able to play any ROMS of games that haven't been released in your hardware's region. You also can't modify the ROMs without stripping the Nintendo signature and thus making this method no longer work.
*But since the 3DS can't tell the difference between this and a real cart, it means Nintendo can't block it with an update, right?
No. Nintendo can and will block this device. Currently, the 3DS can't tell the difference. However, it's just not being instructed to check the right things. There's plenty Nintendo can do to identify this device. For only one example, they can check the read speed of the cart and see that it isn't the same as an official card.
Worse, since ROMs can't be modified, Nintendo also can and will simply include the update on future game carts, making it impossible to play those games with the device since doing so would force an update that made it no longer function.
*So what will I need in order to use this to full effect?
You'll need:
1) The device itself
2) One MicroSD card to standard SD card adaptor for your computer, or a USB card reader device with a MicroSD card slot.
3) One MicroSD card of every standard 3DS ROM size - 512mb, 1GB, 2GB, and 4GB
4) A method of getting save data off the cart, storing it for later, and putting it back on the cart (an R4i save dongle, for instance).
*Will this open any doors for better versions in the future?
Nope. Again, because it's running 1:1 copies, and can't run any modified or unsigned code, it won't be leading to better technology on its own. It will, however, serve to motivate those that are currently working to crack that nut in two ways: First, because someone is out there getting a piece of the pie already and potentially eating their sales, and second because people will be unhappy with the complicated way this one works and demand for a proper system will increase.
