The drawback of this system is that it uses a lot of parts (and thus a lot of space and traces), and that it has to be run at 12V. All of the other stuff runs on 5V, so you have two parts of a schematic that interact, both running at their own voltage level.
Two days ago, the Make blog posted a link to the ORB (Open Random Bit), a random number generator housed in a single, 8-pin chip. An 8-pin Microchip microcontroller, to be precise. The 12C671, to be more precise. Which is now deprecated and succeeded by the 12F675 -- of which I have quite a few lying around.
The algorithm is, apparently, so random that it is in use in various security and gambling applications. It's GPL licensed as well. And with a microcontroller that works on 5V like the rest of the parts and only 8 pins, the layout will be much simpler.
So the past two days I have been porting the code over to the 12F675. I will have to test the code, but first I have to build a toolchain on Ubuntu to work with my programmer.