A MRI machine is probably not included in the $99 kit. :)
I was skeptical that simple, unguided tDCS could have significant effects so I searched some more and found a very nice overview paper: http://www.aipass.org/files/TDCS_State%20of%20the%20art.pdf "Transcranial direct current stimulation: State of the art 2008"
The article I linked references lots of research that had shown measurable results, including research on stimulation of large brain areas, which is all that you'd be able to do with this $99 kit.
I was looking for something, anything, that would tell me if there's significant research in the area and if simple procedures that could be carried out using this kit would work.
(Also you might note that the Nature article was linked 9 hours after my post :) In some ways it does give a better overview of the technique, I'd link it if I had found it.)
I was skeptical that simple, unguided tDCS could have significant effects so I searched some more and found a very nice overview paper: http://www.aipass.org/files/TDCS_State%20of%20the%20art.pdf "Transcranial direct current stimulation: State of the art 2008"