You could also hack the kernel to give you some kind of secret shell
using some kind of secret protocol under some kind of secret
conditions.
The real solution, if you're really concerned about security, is to
get someone you trust to check out the integrity of the kernel. This
implies there's some kind of non-trivial market waiting for the right
kind of certification outfit.
I'm afraid I agree with Ted on this one -- a lot of the configuration
options on the current kernel are only useful for kernel hackers.
-- Raul