Yes I have. My friend has one that is both a guide dog for the blind and a dog for the deaf. They are taught to alert to specific sounds such as someone calling their owners name, phone, door, fire alarm, etc
I understand they are wonderful if you do not want to outfit your house with all the flashing lights and other equipment that many deaf use.
My friend finds the flashers are not usable for her now. Her dog even alerts for the baby. Actually 2yo now. Also the dog is a wonderful companion. She is on her second dog now.