The VS Seeker (Art by Ken Sugimori)

The Vs Seeker is a device that appears in Pokémon FireRed, LeafGreen, Diamond, and Pearl. It needs to be charged by walking around. Once it has been used, the batteries need to be charged again. It can be received from a Ninja girl in the Vermilion City Pokémon Center.

The Vs Seeker sends out a signal that allows Pokémon Trainers to find other trainers who want a rematch. In all games so far in which it has appeared, this was indicated by a white speech balloon with !! appearing above the Trainers' heads, though in FireRed and LeafGreen, the exclamation marks were black, while in Diamond and Pearl, they are red.

In FireRed and LeafGreen, a Trainer who does not wish to battle is indicated by a blue speech balloon with a white X appearing above his or her head. In Diamond and Pearl, there is no indication if a trainer does not, they simply will do nothing.

According to the Pokémon Special manga, they were invented by Bill and work by sensing the fighting spirit of willing trainers.

Trivia

• Red and Leaf, in their Generation III designs, wear them on their backpack straps.