From Bulbapedia, the community-driven Pokémon encyclopedia.
A Pokémon Navigator (Japanese: ポケモンナビゲーター Pokémon Navigeetaa), more often referred to as PokéNav (Japanese: ポケナビ PokéNavi), is an electronic device found in Hoenn. It was produced by the Devon Corporation under the orders of Mr. Stone, who wanted to find a way to keep track of a Pokémon's feelings. Mr. Stone gives it to the protagonist of Pokémon Ruby, Sapphire, and Pokémon Emerald for recovering the Devon Goods from Team Aqua or Team Magma. They appear to be small, compact-disk-shaped devices.
In the Pokémon anime, Max has a PokéNav he received as a traveling gift from his parents. The main function is the map which slightly reduced the amount of times that Ash got lost. In the Ever Grande Conference, it provided all the latest battle results along with statistics on each competitor.
They are chiefly useful for Pokémon Coordinators to keep track of a Pokémon's status for Pokémon Contests.
The PokéNav displays a map of Hoenn, along with the current location of its owner.
The PokéNav checks the Cool, Beauty, Cute, Smart, and Tough condition of Pokémon in detail. It can be set to search only through party Pokémon, or all Pokémon owned combined.
The PokéNav will keep track of 69 unique trainers and alert the user when they want a rematch. Appears only in Pokémon Ruby and Pokémon Sapphire.
In Pokémon Emerald, the Trainer's Eyes is upgraded to the Match Call. In addition to the features of the Trainer's Eyes, it allows its user to call anyone who has had their PokéNav registered with theirs, similar to the cell phone feature of the PokéGear. It can also keep track of more trainers than Trainer's Eyes.
The PokéNav will display the Ribbons Pokémon have acquired, either via Pokémon Contests or special events.