Where I live, it requires a prescription to even get the finger pricking supplies. So yes, if an Apple Watch could some day do it without having to go through a doctor, more people would be alerted to blood sugar issues.
As far as the Apple Watch goes with the elderly, well it isn’t designed for people with poor vision. Diabetes can also screw up vision for non-elderly people too. So at the very least, perhaps Apple could take that into consideration and give an option for a different interface for people with poor vision. Also, I personally don’t want to fish through gobs of useless (to me) fitness options and reports. I would like to completely turn off the fitness stuff I don’t need and easily and quickly interface with the health information I do need. I don’t have an Apple Watch, but my Garmin fitness watch is cluttered with fitness stuff and I have to search for the useful health information. Very frustrating, so I rarely wear it any more.
It would be nice to have the medical diagnosis gizmo Dr. McCoy had on Star Trek.