I watch the Hermits play minecraft and they communicate with mail boxes. There is normally a piece of grey wool under the mailbox, but when a package is delivered, the mail carrier has to remove a piece of green wool out of the mailbox (chest) swap the two colors and then place the grey piece back into the mailbox so that the receiver can then repeat the process after they have read the mail.
So using a trapped chest that gives a redstone signal whenever the lid is open to trigger the "new mail" status and a button to "mark as read"
I have designed (repurposed) this super simple piston setup. It doesn't look too bad. There are tons of ways to decorate it according to the environment or each home etc. It doesn't take up too much space...
I also showed a couple lighting examples, the last using the arrow glitch shown by +xisumavoid
earlier today will not work as it emits a redstone signal that powers the upper piston keeping the system in the "all read" state.
(it looks much cleaner vertical than horizontal. Also I spent a couple hours doing edge triggers and whatnots to make toggle style pistons and they were just so bulky for this task.)#Hermitcraft #mailbox #annunciation