The PokéGear (formally known as the Pokémon Gear) is a key item available in the Pokémon games set in Johto. It acts as a phone, map, and a radio after receiving a card to activate the function.
After defeating the Elite Four, the player can tune into special radio channels, called Sounds, that will lure Pokémon from other regions to the immediate area. A Hoenn counterpart is called the PokeNav. When used in the same fashion and obtained towards the beginning of the game, it can match calls and check your map.
The player can also get Gym leader numbers, but the player must get them when they are away from their gyms (Except Chuck and Blue).