I also came across this thread http://www.arduino.cc/cgi-bin/yabb2/YaBB.pl?num=1225292345/8. More specifically the post by mem that suggests using FETs.
Got the FETs today will try it over the weekend and post back here. 
EDIT: I just looked at the schematic for the sparkfun product and it is in fact, for the birectional tx channel, exactly the same thing! ;D