User and resident hacker @Mrrraou has developed a public implementation of the 3DS kernel exploit known as slowhax. This is a huge step forward for the scene, however it only works up to firmware 11.1. While there are no user tools at the moment which take advantage of this development, expect tools very soon which can facilitate DSi downgrading among other hacks.

GitHub Repo
Ongoing Discussion

 

[SonyUSA]

Once a developer implements this into an existing DSi exploit installer (Such as Yellows8's), we will be able to inject and then downgrade directly from a single console instead of having to do the transfer method as described in Plailect's guide! My advice is to get an entrypoint exploit working (See Smea's website) and run HTTPWN on your 11.0-11.1 3DS and download a compatible, exploitable, DSi Ware game before Nintendo pulls them! (They have already pulled the popular exploitable ones already!)