Apple is most likely the best (and most expensive) watch for tracking health. I wrote a lot about the current value and future of watches for the support of remote families. Apple's best addition is the technical innovation to watches and their marketing, which heightens awareness of them.
I don't think the existing premium watches are the best choice for elderly monitoring. This is because they are power-hungry and give too much data and functionality to the wrist (which can be distracting and confusing). This makes it cumbersome for an older person, and the worst part is charging. It has to be charged every day or two, which is too much of a challenge for older people who live alone.
I'm looking forward to the one-month charging watch. RPM support will be needed at nearly every charging cycle, with a tech person talking the patient through the removal, charging, and replacement of the watch. To be fully successful and widely used, we will need Level 1 and Level 2 support (remote and in-person) as well as an improved engineering design for charging. There are a lot of ways this can fail, and until the full use case is thought through for the different demographics that will use watches.