HP48 machines as Serial Port Monitors

[acoto]

It should work. If interface cabling distance/impedance is not too high, it should not affect the communication between external devices.

Just grab a terminal application and try it.
https://www.hpcalc.org/hp48/utils/terminal/

Electrical details here:
https://www.hpcalc.org/hp48/docs/misc/io2.txt

"The serial I/O port allows full-duplex communication between systems at 1200,
2400, 4800, or 9600 baud over wires with RS-232 compatible signal levels.
Available parity settings are: none, odd, even, mark, or space."