Lifeform Analyzer

The Lifeform Analyzer is an equipable accessory that displays the name of rare monsters (Dungeon Slimes, Lost Girls, etc.) and undiscovered NPCs (Mechanic, Wizard, etc.) around the player. It is one of the three parts necessary to make the R.E.K. 3000, with the others being the Tally Counter and the Radar. It can be bought from the Traveling Merchant.

Trivia
The Lifeform Anaylyzer could be a reference to a device of the same name in the movie Star Wars, which is a portable sensor package that could be carried by an individual.