Tell your teammates where you want them to go in a match by simply drawing it to them. Import an overview image of the map (PNG) and then show them their spots by simply dragging the connected player onto the board.
Draw player's pathes with a crosshair pencil in different colors.
Add icons to the board to illustrate grenade or smoke targets.
Uses http://netty.io/ for network communication and https://code.google.com/p/json-simple/ as communication objects.