Resolution Menu

Simple OS X status bar menu app to switch display modes / resolutions, with support for HiDPI (retina) modes.

For quick access, if you have 1 display only, the display modes can be found at the top level of the menu. For 2 or more displays, each display will have its own submenu.
The list of attached devices / supported display modes is refreshed each time the menu is opened; no need to ever refresh manually.
No color depth information is shown; if a resolution is available with different color depths, only the display mode with the highest color depth will be used.
CoreGraphics private APIs are used to access the HiDPI display modes; this might not get this app accepted into the Mac App Store. Also note that CGDisplayIOServicePort(), which is used to get the (localized) name of the displays, has been deprecated as of Mac OS X 10.9 (Mavericks).
To facilitate "Start at Login", the ServiceManagement.framework is used together with a helper app, which should work in a sandboxed environment as well (as long as the app lives in /Applications).

For a command line utility with the same functionality, check out antmd/resolution-cli.

Enabling HiDPI display modes

To enable HiDPI modes on a non-retina device, execute this in the Terminal app:

sudo defaults write /Library/Preferences/com.apple.windowserver.plist DisplayResolutionEnabled -bool true

Then, for the change to take effect, either log out and back in or restart your system.

Just fetch a DMG from the release section section and drag the application bundle to your Applications folder.

You might need to disable OS X Gatekeeper first: System Preferences > Security & Privacy > General tab > Allow apps downloaded from: Anywhere.

Thanks to Alex Zielenski for StartAtLoginController, which ties together the ServiceManagement stuff without even a single line of code (gotta love KVO).
Thanks to ExitMothership for his LED Cinema Display Icon, which is used for the app icon.

Resolution Menu is published under the MIT License.