Seems a little bit "Big Brother" to me. I think employing this type of service would rely entirely on the circumstances. The introverted family member probably really doesn't need their every step and plan monitored. I would not log onto a website or call some 1-800 service with my plans and I would be really annoyed if I had to answer the phone or log into a website every day just so I can go about living my daily life, and gawd forbid I went out of town for two days and now the sky is falling because I didn't pre-arrange this with 1-800-BIG-BROTHER.
My parents are in their 90s. We actually had to pull them out of an assisted living facility because mom became too afraid that the nurses would not come and help her if she called for them. Now my sister lives with them, and she's much better.
I remember how when I was in my 20s, the 'I've fallen and I can't get up' commercials were hilarious. I'm not elderly yet, but I can see it from here.

A couple of weeks ago, I injured my foot, and I really thought twice about going to the basement to do laundry, because what if my foot gave out and I fell down the stairs? Unlocking the front door and taking my cell phone with me resolved that anxiety, but it does concern me about what might happen after I retire, and there's no co-workers to notice if I don't show up for work. A lot of us live in fairly anonymous neighborhoods where we don't know our neighbors schedules, or aren't there to notice if someone leaves for work or not.
Just saying that for elderly people, it may not feel like Big Brother to have a cheerful voice call every morning while you're working the crossword puzzle over coffee, and inquire how you're doing. A lot of fearful situations- falls, home invasion, sickness- become less fearful if you know that help will arrive by 9:30 if you don't answer at 9. Yes, it would be great if family members would call- but if you don't live locally, what do you do if Aunt Emma doesn't answer? Will the cops take it seriously if you call them and tell them she doesn't answer her phone and you want a welfare check done- or will they take it more seriously if a professional service is calling, especially if it has workers that can be sent out, and they're calling from the house and saying they can't get a response? While Mom and Dad were living by themselves, we relied on Meals on Wheels to report if they got there and no one answered...but a driver in a hurry who assumed that they were just in the bathroom could bring that system to a halt. Mom and Dad loved their MoW drivers, and looked forward to seeing George on Thursday.

They really liked to have a few minutes conversation with someone else during the day.