Artemis47, I know exactly how you feel and have the same concerns. One of my daughters visits me every two weeks or so, more often if she can, after an early work finish on a Friday. I would hate for her to turn up one Summer's day and maybe be confronted with a bad smell and a lot of flies. She would probably have a heart attack too!
It used to be the Milkman who would raise the alarm if milk was left on the step, or the postman who noticed yesterday's letters in the letterbox, but delivered milk and post (especially post) are rare these days.
I have considered an alarm pendant or similar but there is nobody I can think of who would be available as a reliable contact. My daughters live 40 and 55 miles away. They can hardly "pop round" if alerted, even if their phones are available when they are sent the alert. Neighbours are elderly, strangers to me and/or disinterested. There is only one person nearby, an old friend a few streets away, who is reasonably mobile and who I would trust with a key (or my Key-box code), and she can be difficult to contact.
My closer daughter and I have discussed the possibility of her "checking in" on me daily by phone, but if I am out/asleep/in the garden or bath and don't hear the phone or notice the blinking message light on my landline, I really don't want her making an unnecessary 80 mile round trip.
I have decided if I think anything is seriously wrong I should try and get to the pavement outside my house in hopes that somebody might be passing or hopefully I might be able to call an ambulance and get the front door open before I collapse. If I pass in my sleep, (my preferred way to go), there is nothing I can do.
It is one of the reasons I turned down the offer of a kitten after my cat died in 2021.