SdrDx is a free software defined radio application that was originally written to support SDRs built by RF Space. However these days it appears to support multiple other SDRs including the Funcube, Andrus, Peaberry/Softrock and AFEDRI SDRs.
In the latest update they have also added support for the RTL-SDR on OSX. An RTL-SDR dongle is able to connect to the SdrDx program via a special OSX based RTL-SDR server called CocoaRTLServer. At the moment it appears that rtl_tcp is not supported as it does not use the protocol required by SdrDx, so Windows and Linux computers cannot use this software.
Compared to other general purpose SDR receiving software SdrDx has some interesting features not seen in most SDR software that supports the RTL-SDR. The full feature list and list of currently supports SDRs can be found here.