I have been following this thread with interest.
I used to go completely "offline" in old times (cellphones were not so usual). I really wanted to disconnect from my hectic routines and having a “time off”. I just mailed family from time to time, from cybercoffees or shared albergue desktops, and they were not particularly worried about my safety. That they knew that Spain is a safe, modern country with efficient police and health care, helped, too. And, anyway, if something serious happened to me, what could they realistically do? The first 48 hours after any incident are crucial, and there was no real chance of a relative travelling to Spain in less than that.
Lately, as I grew older, with some minor health aches and pains, and I developed a penchant for less travelled, lonely Caminos, my sons insisted that I carried a cellphone, and it seemed sensible to me. But I would hate the idea of having to report home every day; all my experience would revolve around this, worried about if my cell has battery or not, looking constantly for a wifi place, etc. And if I fail to report, I would feel kind of guilty, and my family would start to worry.
Experiences (and families) vary, but I suggest that a practical and realistic transaction for anxious relatives could be agreed, for instance "try to report daily, and if not, every third day, as a minimum).