For users where bandwidthd is run on a firewall, a nice
addition would be to be able to watch traffic from
certain IP addresses pass through a different adapter.
For instance, if you have an interface (eth1) connected
to the Internet, and eth2 is the interface you wish to
monitor for bandwidth, then the bandwidth transferred
from eth2 to eth1 (and subsequently the Internet,
incoming and outgoing), would be counted.