[Alan Anderson]

There's nowhere near enough bandwidth in the RC-OI data stream to pass general audio through the IFI radio modem. You could perhaps get sufficient processing power to do a chunky spectrum analysis and send a dozen or so samples per second, enough to make it possible to recognize a Morse code signal at the other end.

If the frequency of the signal is known in advance, I'd suggest detecting it in hardware and just relaying the output of the detector to the operator.