I\'d like to create a virtual monitor driver for OS X. What I mean by virtual is a monitor driver that does not drive an attached monitor, yet fools OS X into thinking there is
https://github.com/mkernel/EWProxyFramebuffer can do what you want. You have to compile it with xcode yourself and to install EWProxyFrameBuffer.kext to /System/Library/Extensions and EWProxyFrameBufferConnection.framework to /System/Library/Frameworks. Make sure all rights of the installed files are 755 and owner/group is root/wheel. Using EWProxyFrameBuffer.app, you can then de-/activate the monitor.