Oh, so this isn't an existing fax machine, then. I suspect that the most common approach is proprietary so someone can't access the fax unless they also buy their software.
The best way I've seen it done is to use both a telent and web interface. (HP does this with their JetDirect stuff.) That way, however you connect to the device, you can get to the setup. For example, if you are connecting to the device through a serial port, you get the telnet session. If you connect through a network port, you get the web interface.
Most fax machines, however, are connected to the PC via a parallel cable. This makes a standard telnet or web interface a little more troublesome but not impossible. (Another reason they go with proprietary :-( .) I'd play to your strengths. If you are more familar with web/browser access, I'd do it that way. If you are familar with telnet sessions, do that; otherwise, do something proprietary. (I'm probably about as helpful as brick on the head.)
James P. Cottingham
I am the Unknown lead by the Unknowing.
I have done so much with so little
for so long that they think I am now
qualified to do anything with nothing.