Definitely useful for some folk with some cardiac problems.
I had a couple of conversations with a devices cardiologist who was just a bit too gung ho for having me look at that option: it's not good for me and they could not get their head round my descriptions of how it would interfere with what life I have left. Carrot Flower Queen, who was present, was very impressed that I kept my obvious annoyance (well, CFQ is an expert in my signs of annoyance) well enough under control.
Useful for some, as I say.