I find it sad/ humourous that open source printer firmware was part of the impetus behind the free software movement, yet it's probably still one of the most opaque areas there is.
It's not quite what you're looking for, but the EFF publishes a list of printers and whether or not they print tracking dots.
What I want is an open source printer--like a reprap, but 2D? Why not? The printers we buy are such obnoxious crap that falls apart as soon as the warranty is over.