How does Dropbox set the App Icon + Move to Dropbox icon on the Mac OS X Finder shortcut menu?

When Dropbox is installed on Mac OS X, it sets the "Move to Dropbox" context menu when you right-click on any item in the Finder:

I would like to set a similar menu item for another native application. Specifically, I need an "Open in AppName" menu item that allows me to quickly open files in an application without using the "Open With ..." function.

I found ways to add Automator services for these activities.

However, they are installed at the bottom of the menu under the "Services" section. They also don't have an app icon , which is the key to quickly visually finding the right menu item in the list.

Instead, I would like to faithfully reproduce the Move to Dropbox menu item:

• The application icon is displayed.
• At the top of the context menu, not at the very bottom.

What method does Dropbox use? How can I copy it for my own application?

Do I need to include the code for this menu item in the application itself?

Is it possible for the user to add such a menu item for any application, similar to the author / services, without touching the application code?