Many years ago I heard about some invisible drink additives that chemistry students doctored each others drinks with at the pub. The result was apparently amusing rainbow effects later in the Gents.
Building on this concept I propose a new brand of animal food for the conscientious pet owner.
of the primary problems with poo is that it is generally brown, i.e. ground coloured. This makes it hard to spot. As such it is possible for even a well meaning dog owner to occasionally miss their animal fowling the ground. Cats are even worse, in that they tend to crap wherever they like.
Feed your animal on Blue Poo pet foods and the resultant bright blue faeces will be easy to spot for owner or other pedestrians. The sign of a conscientious pet owner will be the colour of their pets crap. Well meaning owners will be less likely to miss an incident, and therefore more able to do there civic duty and clean up after their pet.
Even better, arguments about your cats toilet habits with an annoyed neighbour can be quickly ended: Thats not my pets crap in your flower bed my cat only does Royal Blue Poo
Note this is implemented through a tasteless and colourless additive and so the usual range of cow / chicken / rabbit / camel flavours will still be available to your pet. Obviously Blue Poo is only a marketing brand and that a full range of highly visible colours would be available.
In certain countries (Singapore?) I can see such additive being compulsory. Colours would be allocated separately, according to some form of licensing system, such that illegal fowling can be traced back to the owner for prosecution. Of course there would have to be poo police to make sure your animal was using the correct additives and was not pretending to be someone elses.
In less legislative countries the use of Blue Poo is driven entirely by moral pressure.
Other indicator additives, such as perfumes, could also be considered under the same concept.