Write the next one down.
Five free, and the other person never pays.
For couples
Not because either of you is difficult. Because two people remember one conversation two ways, and neither of you wrote it down.
What it is actually for
Living with somebody is a running negotiation nobody writes down. Who is cooking. Whose turn the shop is. Who said they would ring the landlord, three weeks ago, and has not.
None of it is important enough for a calendar and all of it is important enough to resent. That gap is where this sits.
“I’ll do the bins if you do the shop”
The part couples notice
Muddle, the creature in the app, has no idea which of you is right and never takes a side. That is the joke and it is also the design: an app that decided who was correct would be unbearable to live with.
When you disagree, both versions stay on the record. Nobody is proved wrong. You just pick which one stands, and the history shows it changed.
What it costs
They do not need the app at all. They tap a link and answer. If only one of you is the sort of person who writes things down, that works fine, which is the common case.
Five free, and the other person never pays.