The Camera Lucida is an optical device that was designed by Sir William Hyde Wollaston and used a prism to project an image onto paper for tracing. Some claim that many of the Old Masters used them but they now are only found in antique stores and on EBay. Come Pablo Garcia and Golan Levin who recently teamed up to design the NeoLucida with the belief that it will "profoundly change how people see, how they draw, and how they think about art."
Take a look at their Kickstarter (they have already sold out and have no plans to produce more as of yet).
"We both have a lot of students who’ve come to believe that being able to draw photo-realistically is the most important thing. We both love realistic drawing, but not necessarily the way it’s usually taught which often ignores the tightly-intertwined relationship between drawing and imaging technologies. In particular, art students are encouraged to draw photo-realistically, in the manner of the Old Masters, but without the proper tools for doing so. So we’re producing the NeoLucida as a provocation, not as a business, to help get this discussion started. We hope the NeoLucida will prompt new questions about the relationship of art and technology—and potentially even disrupt business-as-usual in the classroom. Most importantly, we genuinely believe that using a camera lucida will profoundly change how people see, how they draw, and how they think about art." - via their Kickstarter