From the 'why didn't I think of this?' department.
I suppose this product line proves that human evolution is ongoing: Cooler, cooler on wheels, cooler on wheels with an electric motor. But wait, there's more! The arrveedogz have this on their wish list: http://houstontrikke.com.sitepreview.my ... ___dog.jpg
I wonder if you can pull one of those rolling waste tanks behind one of these.