I am looking for a program that can emulate an external monitor using VNC. I.e. the program would add a virtual display that can be accessible through VNC: clients connecting to the VNC would only see this display, not the actual/physical displays. I don't mind about the price. The VNC server should run on Windows.
Use case: I have 2 laptops, one running on Windows 7 SP1 x64 Ultimate, the other one running on OS X 10.10. I would like to use the OS X laptop as an external monitor for the Windows laptop.