I carry a chain whip and cluster socket when touring so I can replace spokes. I made my own chain whip out of an aluminium bar for lightness, and made a metal bar to fit the socket tool so I didn't need a large wrench.
http://www.crazyguyonabike.com/doc/?...oc_id=6089&v=i
I would rather carry a comprehensive tool kit than be stuck on the side of the road wishing I had of.
Make sure you don't overtighten the socket when fixing it at home. This happened to me when I got my wheel replaced on tour and the bike shop tightened the cluster socket so tight that I was not able to loosen it with my tools later when I needed to replace a spoke. I had to go to another bike shop to get them to loosen the cluster.