Matt Venn has got a drawing machine that is rigged as an energy monitor, it looks neat, is in a nice case and works.  Click on this image to see some more.

He has also designed and made all the gear that drives it, it’s an excellent project, and he’s a good guy to talk to about it too.  A continuous monitor of some sort was exactly the kind of thing that I wanted to do with the machine when I started, so I’m excited by seeing this project, and I think my current polargraph software kit is probably open enough to be used for this kind of thing too.

via mattvenn.net