Quite simply, it detects players' lights.
It could be done by creating a radius the size of the player's light around the brick, and when a player enters this radius, it would check whether or not the player has its light on.
Would be useful for stealth mission-type builds.
TALLY CHART OF SUPPORTS. (Because no one else has one)IIIImouse over the tallies if you can't tell what number it is.