I have the same problem you do as well. I probably ask Digi thousands times the same question since I got my Series II module.
Here is my suggestion. PWM0/RSSI(pin6) is an output that shows you the signal strength of your received packet, feed that back into an analog input and sample the ADValue. You will have to come up with the table that corresponde to the dB value.
Let me know if it works. I haven't got a chance to test it out.