Here's a nifty bit of technology for free-hand cutting 2D parts from sheet stock... if you guide a modified power tool, such as a router, within a quarter-inch of the desired cut line, an on-board controller jogs the tool mount to improve the precision of cut:
http://groups.csail.mit.edu/graphics/po ... tingtools/
YT video at:
http://www.youtube.com/watch?feature=pl ... UmL7xZZSUk
Might be an interesting hack using Arduino or Raspberry-Pi, a couple of steppers or tough servos, and line-follower optics/software.
I can see such a system following a printed pattern attached to the stock, but it would be way cooler just to project pattern segments onto the stock from on-board memory somehow, i.e., to give the operator a light-line to follow.
Here's the original NYT article:
http://www.nytimes.com/2012/09/23/techn ... emityn.www