Well, I know of one device which runs FreeBSD and does [I think] what you
were referring to.  I can't find a URL - sorry.  It was a small device
which looked like a print server, did NAT+ipf, dhcp, and a few other
things (DNS?).

I don't see why it couldn't run NetBSD...

My ss5's at home work fine, but they do require some maintenance.  But
they are nicely suited to the task - stable, no console required,
etc...  I'm due to drop off an old ss2 at my parents' house for the same
purpose - just a box which sits in the corner and does its work (and does
it well :-)

-Jon Lindgren
 "Xyzzy!  You're a duck!"
 jlindgren@espus.com, yubyub@yubyub.net