I wonder how hard it is to build something like that using the mic input. Or perhaps measuring the noise on a spare 802.11 card. I know in general it is not easy to add a kernel facility that will be widely available, but how hard is it to build a physical RNG if your specific case demands high entropy and you do not want/need a commercial product?
There is already a project whose name sadly escapes me that does this, using information theory to derive lower bounds on the number of bits of entropy in data read from a line-in jack.
