I have known a few service cats, they were really well trained. they could heal, sit stay, retrieve items on command etc... just like a dog.
I myself had a cat that would go for walks with the dogs even fetching her harness and leash to go on the walks. she would heal, sit , stay, down, sit pretty, roll over, shake hands, fetch, recall, high five, and others that I cannot remember any more. she got a tumer on her brain stem and I had her put down about 4 yrs ago, have not had a cat since then but am almost ready for one. She would also fall sleep with me every night nursing on my arm.