brneuberg

On our last cruise we used the app with the chat feature.   It did not work out well for us with no push notifications.   I found myself using the phones throughout the ship to call into our room.  My lazy teenage son would get a wake up call from "housekeeping" to get up and meet us somewhere.   He would never check the app but always answered the in room phone!

We just all meet for dinner and do our own thing or make specific plan during dinner for the next day.

Google "magnetic dry erase board". Many options available.  Or if you're an Amazon customer, check them too.

I've seen cruisers put small dry erase boards on their doors. The kind with a small dry erase marker holder built in. Not sure if they're held on by magnets or suction cups.
 

Dry erase board on the outside if each other's door.

That's a really great option. I am happy to hear it may not be as rare as it appears!?

We've traveled with family on one cruise and with friends on another.  We made a plan to eat dinner together each day and kind of just decided what to do then, when to meet up, what to do together and what times, we just let each other know our general plans.  Most of the times we just did those things together, but sometimes we might go our separate ways for a while.  I run a business from my phone/laptop and did NOT want to be tethered to them on vacation...so we just used good, old-fashioned, talking to people.  LOL.

Welcome to the forum @brneuberg. All the walls, ceilings and doors are metal. Bring some little magnets to hold notes on the doors...the post its may blow off. Also get some heavy duty magnets like these for hanging cover ups, bags, etc. This will give you a lot more organized storage.
In addition to the apps suggested in @Matt blog, we have successfully used Voxer for several years. It's free, but you can also pay for an upgrade to have a live walkie talkie option. It's available for both Android and Apple. Of course, to use it you will need access to the ship's wifi (Voom).
Happy sailing!

How to stay in touch with someone on your Royal Caribbean cruise