Macos – Auto-hide OS X menu bar

Is there a way to auto-hide the OS X menu bar, like is possible with the Dock?

There was an application "Menufela" that did this for Tiger, but I'm not aware of anything similar for Leopard/Snow Leopard..

I'm almost certain this is (programatically) doable, because in full-screen applications the menu bar is hidden, and reappears when you mouse the mouse is at the top of the screen..

Edit: With the help of Steve Folly's answer, the following code:

[[NSApplication sharedApplication]
     setPresentationOptions:   NSApplicationPresentationAutoHideMenuBar
                             | NSApplicationPresentationAutoHideDock];

..will auto-hide the menubar (and the dock, as mandated by the API), but only for the current application:

When controlling or disabling features of Mac OS X system using SetSystemUIMode the requested behaviors are only in effect while the process which called SetSystemUIMode is frontmost

..close, but not quite there