We had a pretty good idea of what BD&A's Guitar Hero stylus accessory would look like, but we figured there was always the possibility of a surprise until we could see a picture of the thing. A picture has just been added to the Gamestop listing, and there is no surprise to be found.
The DS Lite Guitar Hero Stylus is exactly the same idea as the Jammin' Guitar Pick stylus that Naki released to go with Jam Sessions. It's a stylus attached to a guitar pick. You hold the pick and use the stylus end on the screen, which sounds, at least, a little more guitar-like than just playing the DS with a little stick.
The major differences between the two products? The Guitar Hero set has the Guitar Hero logo on the picks, and doesn't come with as many.