Mike Stewart (founder of Wildrose Kennels) has been breeding/training diabetic alert dogs for decades. Amazing to watch one react to an alert.
Dogs have been trained for many service related activities.
I once had a State Department service dog and handler onboard one of my flights. They were heading to an international location ahead of the SoS. The dog had a very specialized skillset associated with its nose.
My dogs are "watchers". Not much escapes their attention, regardless of the hour.