I saw a film once with Sir Anthony Hopkins about the guy who invented Kellog's Corn Flakes. Dr. Kellog I think his name was. Anyway, I remember he had a sanitorium and he diagnosed peoples illnesses by examining their stools.
This was set in the US in the 20's I think. So they look at poo as well. It seems to be a universal thing.
I've never seen the utility of it as a health check myself. I mean, given that my diet changes how do I know what colour it should be.
Anyway, I would need some kind of a paint-chart to measure the change. "Today it's ochre number 4, but yesterday it was more Oak Bark 3, therefore I must see a doctor!"