Alakazam demonstrated this at Tabula Mentis last Saturday. I've just seen one on sale at World of Magic for £289.25!!!!! (
http://www.world-of-magic.co.uk/Cobra_S ... i21258.asp )
I decided to price up the parts for one. Now, unless I've missed some clever piece of gaffing, then including a rechargeable batter and a Sharpie, the parts are available for less than a tenner. The principle is electric not "electronic", by the way.
If someone has a Cobra Sharpie and can demonstrate that it's far more clever than I believe, I'll gladly delete this and sing its praises, but at the moment it screams "rip off!".