The image is a joke, and is a gross misrepresentation of how it works. Well, almost.
NTRBootHax, formerly known as MagnetHax, has been released for public usage.
Earlier this year, with a combined usage of a Magnet and a NDS Flashcart, @SciresM demonstrated in a video that he gained early access to bootrom of the 3DS.
This method is also said to be able to salvage 3DSs' from the hell, that made them effectively a brick.
A magnet is only required for models that can be "flipped shut"; 2DS (non-XL) doesn't require this.
Possibly due to an oversight by programmers/hardware developers, the 3DS checks to see if Start+Select+X is held down, and if the shell is closed.
If so, the 3DS will attempt to boot from an NDS cartridge from the bootrom (with bootrom access).
Hence, the purpose of the magnet is enable a state that the 3DS believes that the shell is closed.
With this hax, it'll allow the use of save editors like PKHeX and ROM hacks using HANS.