These items, created by the Mountain Elves of Argalen, are highly prized by military commanders. While far from common some are in the possession of human and gnomish leaders as gifts, others are in the hands of human, orcish, and hobgoblin forces as spoils of war.
While they vary in appearance they are all open faced helms with cheek plates and nasals giving the head a base A.C. of 2. The helms make all saves at +2 but grant no bonuses to their wearer. The helmets will resize themselves to properly fit any humanoid (or creature with a human-like head!) from brownie to ogre size
The helms are enchanted to allow a wearer to speak to another wearer up to three miles away. All communications require that the person sending the message have a clear line of sight to the receiver and actually be able to the see the target. A person can receive a message at any time but may only send when observing the target recipient.
The magic of the helmets ensures that the message can be heard over the din of battle but deafness effects (from a spell or, say, a dragonne's roar) of course prevent someone from hearing the message.
Only one person may be spoken to at a time (no 'broadcast messages') and only 3 people per round can be spoken to.
Their utility on large battlefields should be obvious.