Of course, there are R/C simulators for MacOS, not so many as for Windows, but still:
1) Commercial sim X-Plane, which has a couple of R/C models
2) Freeware Slope Soaring Simulator

In order to interface your transmitter with these simulators, you should use a Transmitter-to-USB interface. Just stay away from Serial PIC interfaces with integrated USB-to-Serial converters. These "quasi USB" interfaces are only supported by FMS, CockpitMaster, and RC Plane Master, which only run in Windows.

A true USB interface is supported by all simulators (not counting those, which use their interfaces for copy protection, like Reflex or AeroFly Pro) and works in both Windows and MacOS:
[link=http://www.milehighwings.com/sim_compatibility.htm]Milehighwings.com Interface Compatibility[/link]