Feng Shui: The Lost Island
When groups of friends talk, the mess of in-jokes, references, and innuendo can be virtually impenetrable by outside sources. With this schtick, the group may communicate in plain sight, even during a fight, without any onlooker understanding what’s being communicated. The group may use any combination of gestures, codewords, handshakes, chicken scratch, rolls of the eyes, or anything else they like. A number of words equal to the “speaker’s” Charisma may be transmitted; a number equal to the “receiver’s” Perception are understood (GM decides which words).
Once an onlooker realizes that coded signals are being sent (after at least three or four messages have been sent between any group members in their presence), she may attempt to intercept signals using her own Perception.