This addon isn't being developed anymore, but still works by changing addon.xml's python requirement (2.0 --> 2.1.0) and having wicd (wicd-curses) installed (on Linux) and removing network-manager. If you're new to wicd and trying to get it working right: run wicd-curses, Preferences > Advanced, then change from wext to nl80211.
Attached add-on version that has the modified addon.xml, STOP AUTO function (which causes problems) has been removed and the no background GUI on non-confluence skins has been worked around.
It doesn't close properly, and the stop auto messes things up.
There's a successor addon called 'Network-Manager front-end for XBMCbuntu' but I couldn't get it to work right, so this one is what I'm going with.
Addon - https://github.com/vikjon0/xbmc.script.linux.wireless
Addon's release/old support thread - http://forum.kodi.tv/showthread.php?tid=...light=wicd
I am using it because I need a way to configure wireless using only a game controller, which means being able to select the correct scanned network and enter the passkey with the on screen keyboard. OpenElec works great for this with their configuration utility, but I'm using it for a raspberry Pi, which is built differently and doesn't have support for gamepads (at least for the PS3 wireless controller).
If there's an alternative that I don't know about, I'd love to know.