My sisters dog is insured by More than I think it is...
What they have given her is a tag which the dog wears at all times, which means that if it is involved in an accident or needs veterinary attention at any time, the vet can perform any work necessary without needing to speak to my sister first as the tag means that all work undertaken by the vet is covered automatically by the insurance.
It is highly unlikely that she will ever need this, touch wood, but I know my sister liked this option and it gave her peace of mind.