Animal BehavioristsPets go through separation anxiety and experience fear of thunderstorms and other loud noises. They can act a bit anti-social by biting and soiling in the house, and have neurotic behaviors, such as obsessive grooming. Behaviorists help owners solve these types of problems and are also involved in obedience training.
A background in psychology and/or education would be appropriate for the assistant behaviorist jobs that are available with larger practices. The retail industry is also devoted to marketing training devices and accessories, such as invisible fences and no-bark collars. See AnimalBehaviorCounselors.org.
Entrepreneurs
Countless pet owners are gone from home 10 hours or more. Who's going to walk and feed the dogs and kitties? Who's there to spend time with lonely pets? If you have an entrepreneurial spirit and there's nobody in your community offering these services, it could become your perfect niche.
Another idea: become a pet chauffeur to help the elderly and infirm and others who don't drive get their pets to and from vet appointments. Take a look at Pet-Sitters.biz and PetRide.com.