Dragon Quest VI
This skill appears in the original and DS version of DQVI, as part of the Thief skillset. The chosen character needs to win 44 battles, obtaining a total battle count of 110. It costs zero MP to use and displays the current number of treasure located on the dungeon floor.
Dragon Quest IX
Nose for Treasure is also an ability in Dragon Quest IX. A Thief can get it by putting 42 skill points into Acquisitiveness, but can subsequently use it in any other vocation. It will notify you of any red treasure chests in the area (In other words, tell you if there are any).