Just been pondering this triggered by many comments on another thread (where the poster lived some distance from parents) suggesting a lifeline button.
But with the button, someone has to be the person on call, & it's a pretty big commitment.
I've also wondered (I know, I could ask, but there's not much I can do if there's no good answer) what happens if my parent presses the button & I'm not available. Luckily so far that's not been the case (& very kindly neighbours have covered the couple of times we've been on holiday), but it easily could.