I have a dog that I would LOVE to train to be a service dog.
He already does most of the things already: comforts me, allows me to drive for errands, nudges and encourages me to get up when I'm depressed, braces his body for me to pull myself up, braces and stands so I can lightly sit on his rump and regain my energy during walks, brings me things, watches the front door, runs through my house on voice command to check for intruders...
I've already managed to teach him to open the fridge since I read this thread, he's eager to learn and "help his mommy". :)

Cheers
Y&A