My mother has no idea how to check her email and doesn't use it. She also doesn't know how to text. Or check voicemail. It's just another point of anecdata, but this is my bar for "non-technical."
I too have struggled to establish private communications with nontechnical folks.
I think the best bet would be to create a device with the sole functionality of establishing an encrypted voice line to you. Essentially, a plastic brick with an on button, speaker and microphone. No screen, no UI, just on/off. Like a walkie-talkie, but for infinite distances.
I think the best bet would be to create a device with the sole functionality of establishing an encrypted voice line to you. Essentially, a plastic brick with an on button, speaker and microphone. No screen, no UI, just on/off. Like a walkie-talkie, but for infinite distances.