In accordance with G29, devices capable only of outbound communication would be permitted in the castle. Thus, the microphone end of a baby monitor, for example, would be permitted in the castle. Such a device could be used to send commands or questions to the Spy, who would be in possession of the receiver. If the Spy were to give an unclear gesture, the drive team could ask for further clarification. If visibility were poor, the drive team would be able to ask the Spy to point to a boulder or to alternatively indicate the position of an opposing team member. Overall, the drive team would be able to receive desired information without the Spy having to guess what it is that the drive team wants to know at a given time.
G29:
During a MATCH, DRIVE TEAMS may not use electronic devices which have the capability of receiving communications from persons outside of the CASTLE (e.g. cell phones or wearable technology). Violation: Yellow Card
I wouldn’t count on that rule lasting for very long. The reason to enforce no electronic devices is to prevent interference and for safety reasons, such as a ref yelling at you because something is about to hit you, but you can’t hear them because you’re wearing an earpiece or you have something blaring into your ear.
I think it would be easier to just give the spy a white board for communication. Which I’d assume is allowed, as it wouldn’t cause any interference or safety hazard, like RyanN said.