I've ported a few of the FreeBSD tools for ath and 802.11 monitoring.
Testing thus far has been minimal.  You can find them at
http://www.machshav.com/~smb/ath-tools/.  I have not attempted
to figure out where they should fit in our source tree, nor do the
#include files reflect any location in the tree.  My testing was
done on 3.99.9 from about a month ago.

80211debug has a problem with its sysctls; I neither know what
it's trying to accomplish nor do I know what a % in sysctlbyname means
in that version of FreeBSD.  (I can probably figure it out now that
I'm back online, but I did my work on a airplane...)  80211stats
has lots of undefined symbols, and I haven't found where, if anywhere,
NetBSD keeps its equivalents.  It's possible that 'ifconfig -v'
subsumes it.