I attempted a port of the wireless "Enhanced SSID security patch" from 
http://wleiden.webweaving.org:8080/svn/node-config/other/enh-sec-patch/ 
- which allows disabling SSID broadcasting - to FreeBSD 4.9.

While I think it worked and I can successfully set that ENHSEC RID with 
wicontrol (and then don't see the AP anymore on my PowerBook), I've run 
into another problem: ENHSEC only works with firmware 1.6.3 and above. 
The only public firmware versions above 1.6.3 that I could find were 
1.7.4 and 1.8.0 (well, 1.7.1 too but apparently it wasn't compatible 
with my card). But those firmware versions don't work properly in hostap 
mode with FreeBSD 4.9 anymore (clients cannot associate); I think this 
has been reported before.

So it seems like we're stuck in a dead end as far as disabling SSID 
broadcasting is concerned.

- Manuel