Player N°1 wandering in the Wasteland.

Player N°1 listening to radio channel xx.

Player N°2 asking for help on radio channel xx.

Player N°1 receiving distress call : as he is connected on channel xx, HE CAN SEE Player N°2's location on WM.

Player N°1 rejoining Player N°2.

There could be a special command to indicate my location. For instance "/P" at the beginning of sentence (to avoid being located while i just want to talk on radio).
When the player who communicated his position leaves the area, the marker map disappears.
Restriction possibility: To receive the distress call location Player should have 100 or more in outdoor skill. Or,it could be: the less you have outdoor, the less chance you have to receive the distress call location