This is the approach taken by mgetty/vgetty. It creates a file with the
output of ATI6 after each call. VERY handy, since the modem can tell you
a little more about why it disconnected.
I suppose this could be hacked with in.pmd and radius modifications to
trigger a chat script whenever a disconnect occurs.
Sounds messy tho-- It would be nicer if comos could report this to radius
itself :-)