I have had two service dogs who alerted me in advance for PCS onset which can include small seizures. I think that it works or not by how much you are in tune with your animal. I have a cat who is my buddy, and he is better able to alert me than the 2 service dogs (one of which has passed). Unfortunately, the ADA will be officially changed on March 15 2011 to exclude all animals to be considered service animals except dogs and small horses. As usual, cats and ferrets are underated, even though I know of many disabled people who are helped by these animals by alerting to conditions including medical, and fetching etc.