USB I/O via R (Charly)

By way of closing the thread and thanking Charly for the suggestion.  
RPy did turn out to be the easiest solution for accessing the serial  
hardware from within R, and by calling the routine from within R via  
system(python ...),  everyone is happy.

A word to anyone requiring a hardware interface for data  
acquisition:  When I flush the input buffers using the  
serial.Serial.flushInput() method in the pySerial library, it   
appears to permanently shut down my Mac serial ports. This was  
independent of device and driver (it occurs with direct USB and over  
a prolific USB-serial converter), and it is easily avoided by not  
flushing the input buffer, if  compatible with your application. I  
have not tried other serial libraries, such as USPP or pyVisa. I  
know this is a question for the Python list, but is worth keeping in  
mind when selecting your external interface.