I am trying to add a functionality to my status bar app for Mac OS X. I would like to be able to move my item along the bar, as you can do for the native OS tools like the Bluetooth or the WiFi icon.
Cheers
What you are looking for is NSMenuExtra and not NSMenuItem.
Apple uses NSMenuExtra for the system menu icons including Wi-Fi and Bluetooth. Although it looks similar to the regular NSMenuItem, NSMenuExtra has some special features, notably to keep their relative order after rebooting, and Command-Draggable by user.
Unfortunately, NSMenuExtra is totally undocumented, so if you are targeting the Mac App Store, it's better for you to stick with the standard NSMenuItem. Otherwise, there is a bunch of tutorials about how to create an NSMenuExtra. For example, here are two of them: