Those things have one pretty serious drawback: falls tend to happen while the person isn't wearing it. Of course, this might not be any different for smart watches and such.
What's the state of the art with "Hey Siri, I've fallen and I can't get up"? That sounds like something that, if coded, is always there for you if you need help. I suppose there could be some sort of gas release that renders you unable to speak, but on the other hand, that seems rare. If you fall down the stairs, that sounds like it would work, and you don't need to remember to wear anything.
