The "cabin ready" is something that the flight-attendants notify you verbally about.
We have decided to NOT add any of the automatic callouts that co-pilots or flight-attendants do, as opposed to other dev teams, because the procedures and wordings vary too wildly and instead of people being happy, it would trigger an avalanche of people requesting to do it this way or that way, because when they flew as kids in the 60´s they alwas used to hear "fasten your harness", but now they say "seatbelts" and how on earth can they expected to enjoy the 737 with such a glaring discrepancy...