SprayPen

Whatever happened to the spraypen?
I was reading about it in the ‘Design Rendering Techniques’ which undoubtably most of you have at least looked at.
Well right after he describes the air-brush and the letrajet (spraymarker)
he talks about the SprayPen as being a wicked tool that will replace the airbrush since it doesnt need a compressor, you just insert the marker and by static electricity it propulses the ink. (page 20 for all who have the book)
and there’s an illustration of it on page 21.

So my question is… what happened to it? did it never take off? where can I buy one? looks like an amazing gadget.

Thanks for all the replies.