Adding /usr/local to daily security audit

Is there an easy way? Mainly just want to check the binaries, libraries
and config files under /usr/local.  Doesn't need to be at the same level
as the default /usr/pkg audit, maybe just daily checks of
/usr/local/{bin,etc,libexec}, log diffs and generate/check checksums.  As
near as I can tell I'd probably need to create something in
/etc/security.local and maybe a permissions category under /etc/mtree/.
But I'm not sure.  Maybe there's an easier way.  Didn't see anything that
seemed relevant on netbsd.org; maybe someone knows of other online
resources that cover this topic?

Jeff W.
Albany, OR