The opportunity.
We capture more of our lives than any generation before us, and we revisit almost none of it. Photos are increasingly performed and chosen for how they'll look. What almost nobody captures is how a moment actually sounded: the laugh at dinner, the dumb voice your friend does, the way your mom says your name. Audio holds the feeling a photo leaves out.
People already want this. Homemade iPhone shortcuts record a voice memo, bury it under a random date weeks out, and send it back when that date arrives. When people hack it together with automation, that's a product nobody has built yet.
Record a moment now, forget it, and have it come back when you least expect it. Not a journal, not a social feed. A time capsule that opens itself.