RF Explorer has now a working version for Mac OS, thanks to the great job done by Dirk-Willem van Gulik. Kudos for a nice looking tool!
Note this is a work in progress and you will need to upgrade to firmware v1.08 Beta 02 to use this as the current RF Explorer firmware v1.07 available doesn't properly handle baudrates accepted by MacOS Silabs driver.
Visit his site at http://dirkx.github.com/iRF-Explorer/