Sounds like one of those nutty snake oil things but it seems they've got lots of studies showing it works. It's a $300 device that looks like a walkman with electrodes clipped to your ears for 20 minutes a couple times a day for a week or two. Very mild electrical charge.

http://www.drdebe.com/CRANIAL.htm
http://www.reynoldsoffice.com/1111-2.htm
http://dynamind.com/ces.htm#hpax

Um, on looking further it doesn't seem to be mentioned as directly improving ADD symptoms but supposedly a miracle cure for insomnia, pain, depression, anxiety, etc. It is sort of along the same lines as EEG Biofeedback which has been used for ADD with moderate results.