Try using the Get HTTP Request Value component (which is only usable in a Web Forms or WF type project). Specify REMOTE_ADDR as the Request Variable To Get.
If this comp happens to spit out an IP, just use Get Computer Info with this IP input (or you could use the Get Computer Name By IP Address in GeneralNetworking DLL)
REMOTE_ADDR can be spoofed in a request but shouldn't be an issue for the average application.