Figure out what the monitor will do

The "monitor" is the computer that displays the game. Whilst the smartphone ("controller") is only visible to the individual player, the monitor is a place for general information to be seen by everyone.

However, this game is about exploration. At the start, no part of the map is visible, nor any of its properties. How does this change over time? What is displayed on the map?

Whenever an island is discovered (and claimed), it is revealed (??)
There's a "sea radio": whenever something happens, it notifies everyone in vague terms. ("Someone discovered an island!"). When nothing is happening, it drops hints. ("There's treasure to be found in sector 1 or 3.")
Through the map, one can see little dots. These can mean anything: a monster, another ship, a dock, etc. You only know what it means once you get close enough.
Everyone can see the "trade offers" at the docks, or the locations of landmarks (once discovered).
(Optional) Moving units leave trails (like the "fading footsteps" from that magical map in Harry Potter), you can follow these trails.
(Optional) A person in need, who has been thrown overboard, will emit a danger signal.

These are all good ideas ... but I need something more. There needs to be a very good reason for there to be a monitor. It mustn't just look nice (once the map is more revealed and there are many moving parts), it must serve the game.

Some ideas:

There's a cloaking mechanism. Ships can go "under the radar" (or "lights out"), or masquarade as someone else, but only on the monitor.
There's a WEATHER system. On the monitor, there are clouds hanging above the map and you can see what the weather is doing (which will most likely determine if you want to go somewhere or not)
It helps with long-range attacks or triggering "mines". On the monitor, you can easily and precisely see where someone is located (like B4 or G19), and thus target them better.
??

Pandaqi / In-the-Same-Boat

Figure out what the monitor will do #7