This mod adds commands and items that allow you to bring attention of other players to a specific point in the game world. You do this by placing a temporary HUD waypoint that's visible to everyone within some radius.
To place the waypoint you can point your crosshair at something (can even be just terrain in the distance) and type:
/look! [your message here]
A waypoint will appear that will be shown to other players, together with an arrow pointing towards it.
If you can't point your crosshair beforehand (or it's too dangerous to stand in one place and type the message), you can "prepare" a command beforehand and then "place" it later. To do this, first type:
/look [your message]
Your message will be saved, and now you can run and look around, but
punch the waypoint will be placed where you were pointing
punch action. If you decide to not put the waypoint, you
place to cancel.
Craftable item that does same thing as commands, but allows you save some typing. Craft a flag tool from sticks and red wool.
You can then press
place to place a waypoint where you're pointing
at. You can also press
sneak+place to open a window where you can
edit the default message the flag will add to the waypoint. This way
you can prepare multiple flags with specific messages and quickly
command a group of people during battle.