What a great story! A few people in a diabetes group I belong to said that their dogs (and I think some of their cats too) act differently when their glucose levels go out of whack.
I have also seen news stories about a dog that predicted heart attacks (1st his owner, and then others), and there was a great story in Guideposts magazine about a woman who didn't know that she stopped breathing many times each night, and her dog woke her up each time. She thought the dog was just being a nuisance until she found out the truth in a sleep study.
It is amazing how in tune to us animals can be.
I almost forgot, I saw a news story a week or so about a cat at a nursing home. This cat doesn't have anything to do with anyone--until they are within hours of dying. Then he cuddles with the person. They said he is just about always right (something like 25+ times now), so when they see him go to a patient, they call the family in. I figured that if it was on the TV news, it might have also been in the paper, so I just did a search. Here is an article about that cat. His name is Oscar: FOXNews.com - Oscar the Cat Predicts Nursing Home Deaths - Health News | Current Health News | Medical News