A company called Datel has released software for the PC called My Mii Manager that allows you to edit your existing Miis and create new ones.
Truth be told, you can already work with your Miis by importing them onto your PC using a combination of steps that you can follow here (and oh yea, you’ll need a bluetooth USB unit to do it). Once you get your Miis onto your PC, you can even use the cool web-based Mii Editor to edit those files.
Probably the coolest thing about the My Mii Manager is that it comes with a bluetooth adapter that works with the software so you don’t have to worry about getting the right stack for your current bluetooth adapter and piecing everything together.
And for $20 for the whole package, that sounds good considering prices for a bluetooth adapter alone.
If anyone ends up trying out the My Mii Manager, please let us know how it turns out!