I saw some sort of "miracle pets" TV show (I don't remember if that was the exact name) where this woman had a "working dog" that was trained to sense when she was about to have a seizure, and then to help her around the house after the seizures happened because she would be partially paralyzed for a few days/weeks after an attack and would have to use a wheelchair. So this dog would jump up on her chest and stare into her face and wouldn't leave her alone until she lay down on the floor somewhere that her thrashing wouldn't hit anything.
But that wasn't the amazing part. The woman also had a form of sleep apnea (dunno if I spelled that right), which means she would sometimes stop breathing at night. The dog was also trained to start barking when she stopped breathing so she would wake up. She had just bought a machine, though, that was supposed to strap to her face and supply her with oxygen all night, so she gave the dog the command that told him he wasn't supposed to bark at night. She strapped the thing on her face and went to sleep, looking forward to her first uninterrupted night of sleep in a long time.
When she woke up, she saw that her beloved dog had chewed through the hose and ruined her expensive piece of breathing equipment! She started to yell at the dog, then she noticed her alarm clock was blinking 12:00. The power had gone out during the night. The machine needed an air-tight seal to work, and without power it wasn't able to circulate the air and started suffocating her. The dog, who would have barked, had it not been commanded to be quiet, instead chewed a hole in the hose, probably saving her life.