We've seen (and considered designing our own) chain keepers for doing maintenance before. They typically seem to run about $10–20. A buddy of a buddy of a guy who knows a guy who knows this mechanic (Paul from Bike Tech Miami) who made this simple version from a derailleur pulley and a chopped quick-release skewer:

From Paul: "I got it from this old school cuban mechanic. His name is Kiko Martin. Thanks for posting that, cool"

This sort of thing is super-handy for the folks who want to clean their chain with the wheel removed (and also want to protect the chainstay). Also, I've used a similar apparatus for packing up my S & S coupled Travelers Check to keep the chain in place while smooshing Swiss Cake Rolls and dirty socks around the components...