[ale] versatile bandwidth monitor

[jb at sourceillustrated.com (John Wells)]

I'm now under a service agreement with my VPS provider, and I'll get
charged each month if I go above and beyond a certain bandwidth limit.

As I run multiple domains and also transfer via other methods (email, ssh,
scp), I'd like to find a versatile bandwidth monitor that can run as a
daemon and collect stats over time.  Anyone know of such a beast? 
Ideally, it could also track bandwidth down to a domain (email and http)
level, perhaps via log files.  It could also track bandwidth via ports, so
I could know how much SSH has come in.

Any ideas?  Any combinations of existing tools that will do this?

Thanks!
John