The Slate Monitron is a special piece of wargear used by the Tempestus Scions of the Militarum Tempestus, usually worn on the right armoured forearm gauntlet in what is known as the "Dextera Configuration." This data-slate allows the Tempestus Scion instant access to his Tempestor Prime's latest command runes and war psalms.
It also monitors vital signs, showing the pulse rate and health matrix of the wearer at all times so that his officer can instantly assess his condition. It was the Slate Monitron that led to the old Imperial Guardsman jibe that Tempestus Scions are dead inside, for upon completion of their training their hearts are locked in an iron box mounted on their sleeve.
- Codex: Militarum Tempestus (6th Edition), pg. 8