I did some research today and found a plug in fuse/switch at RV-parts.com ($39.95 US). Company is sending me some photos of an installation on a 2010 Malibu. By removing the fuse it will eliminate battery drain but I am not sure if miles will accumulate on the odometer. I previously towed a 2003 Saturn L200 and removing the ignition fuse kept towed miles of the odometer.
Chevrolet Malibu 2010 tows great. Blue Ox base plate fits with small modification to the grill. Major problem is pulling the ignition fuse. It's smaller than your thumb nail and very hard to get to under the passenger side of the console. Have been many places to look for a switchable fuse so you do not have to remove the console panel every time you tow. Has any one found an alternative?