Reading screen I/O from a remote terminal

[Bob Marley]

I'm trying to find a way to monitor and detect certain strings
that have been written to stdio. What I essentially want to do
is dialup a host, via telephone, and automatically keyin sequences
according to what the appropriate keyins should be (if they were
to be manually done).
I know how to do this on a PC by threading into the modem line and
looking for character sequences, but does anyone know how (if possible)
I would be able to do this on just a standard Unix terminal?

Thanks
LJF