Minecraft wiki entry for Development_versions, associated text: Gives out a signal depending on the amount of players looking inside. 1 person = 1 strength signal, 2 people = 2, etc.
Crafted with a chest and a tripwire hook.
Large trapped chests can be staggered with large chests to allow more compact storage.
Texture is slightly different than a normal chest, with a red stain around the latch.