See here for details and concept: http://mke3.net/archives/2006/07/radiation.html

Previously, my method of temporarily holding down a key to access the menu was severely limited by the fact that although Blender can detect when modifier keys such as Ctrl/Shift/Alt are held down, it didn't have that capability for other normal keys on the keyboard - holding other keys down would send repeated events, and overflow the queue.

According to a conversation we had, Jean-Luc plans to work on adding this capability to Blender when he works on the events system, so I'd resigned myself to waiting until then. However he's probably been busy and hasn't been able to make much progress on this particular part, so I wrote some temporary code to work around that and provide this functionality in Blender. So now, these menus are accessible from any hotkey. Also improved from my previous blog post is the ability to have more than 8 menu items, which is needed for larger menus. Although menus the size of the current W key mesh specials menu are good for nobody, radial or list.

Anyway, this is the initial revision in patch form, I'm posting it here for curious people to try out. Keep in mind that it's still a bit rough around the edges, particularly with placement of menus with lots of items (which is really a usability fault in Blender for having a menu that big, but anyway...)