Just a heads up for other people interested in this:
I also tried keylaunch (apt-get install keylaunch)and it works fine with some modifications to the instructions linked to in Sho's post:

• I head to use "xset770 -r 135 0" to disable key repeat for Chr (Multi_key).
• In /etc/keylaunchrc: key=....Pressed Multi_key:~/usr/share/keylaunch/xmodmap -e "pointer = 2 3 1" and key=....Released Multi_key:~/usr/share/keylaunch/xmodmap -e "pointer = 1 2 3"

I did not integrate it into the init files yet, since I am not too sure if I would rather keep the symbols behind Chr.

And Bundyo -if your are still reading this- navigating java script sub--menus after right-clicking is pretty much hit or miss since it interferes with scrolling. Maybe the keys on the D-pad can be used to move in such menus? Or if a simple click on the menu entry to open the sub-menu wouldn't cause the whole menu to disappear would be better. I'll file a formal bug report, if you think that this is important enough for tear.