I don't think so. What you're thinking of is an Open Firmware program that behaves as a telnet client. I suppose someone could write such a program but it would not be useful. Plus scrolling is really slow in Open Firmware.
The purpose of the io command in Open Firmware is to redirect input and output.
You can use the input and output commands just to redirect one of them.
Usually, input defaults to keyboard and output defaults to the screen.
Use the printenv command to see the current input and output settings.
http://www.firmworks.com/QuickRef.html
