This is a tool that lets you use MacBook Pro Retina's highest and unsupported resolutions. As an example, a Retina MacBook Pro 13" can be set to 3360×2100 maximum resolution, as opposed to Apple's max supported 1680×1050. It is accessible from status bar.

For more practical results, add RDM.app to your Login Items on System Preferences ➡ Users & Groups ➡ Login Items. This way RDM will run automatically on startup.

This software was studied and released here and here by its original authors. I just improved the build systems and Makefile, fixed the icon, added support to easy installable package (PKG) and improved the way menu is displayed. I don't know what is the license by its authors because it came 100% uncommented and undocumented. But I'm sure they would enjoy you to freely use it. Me too.

Want installable binary package? It is here.