A private assistant for one household, run on a server in that household's home. It gathers what the family would otherwise drop: school emails and the dates inside them, flights and exams, household services and invoices, bills and deadlines, and messages that have gone unanswered.
It has one user, the person who built and runs it. It is not a product, it is not for sale, and nobody can sign up for it.
With the owner's permission it reads his own Gmail and Google Calendar, alongside his own calendars, bank data and home systems. Everything it reads stays on his own server.