And then pay somebody to guard it. Aka the "pay someone else to do it" option that your sibling comment talks about (and of which there are many different flavors, S3 being another one).

I'd prefer a mobile solution. Something I can just put into a box and forget about. Someone else can than stumble upon it and be able to read it.

Basically like a box of photographs. But I know that's a foolish dream to have.