I honestly don't know, OpenBSD has an
iwn(4) driver.. but I can't seem to find that via FreeBSD man pages.
Try looking
here though, Damien seems to be the author of the driver.
EDIT:
http://www.clearchain.com/wiki/Iwn -- "A majorly updated version of the iwn driver has been committed to FreeBSD -Current (aka 8.0)"