Poké Radar
From Bulbapedia, the community-driven Pokémon encyclopedia.
The Poké Radar (Japanese: ポケトレ Poké Tore) is a key item in Pokémon Diamond and Pearl that is used to seek out wild Pokémon hiding in long grass. Like the Vs Seeker, its battery must be charged after use by walking around. It takes fifty steps to fully charge the Poké Radar.
After the player has seen every Pokémon in the Sinnoh Dex, they will be able to meet Professor Oak in Professor Rowan's lab in Sandgem Town. After upgrading the Pokédex to the National model, he will also give away the Poké Radar, but will not explain it very thoroughly.
It can only be used in the standard tall grass, while on foot, at which point, a tune will begin to play, and one or more patches of the long grass will begin to move. Patches that shake more violently than others are oftentimes more rare Pokémon, including Pokémon exclusive to the use of the Poké Radar. When a player walks into one of these moving patches, a battle with a wild Pokémon will instantly begin.
If the Pokémon that is found is fainted or captured in a Poké Ball, a chain will begin. These chains consist of multiple members of the same Pokémon species (such as Farfetch'd) encountered one after another. The only catch is this: a player must not encounter any Pokémon just by walking through non-wiggling grass, only by walking into the grass that shakes, therefore, it is recommended that Repel is used in order to ensure this and get a higher chain. One of the many functions of the Pokétch is to display the current chain and the three best chains made so far.
Long chains increase the chance of finding a shiny Pokémon, which is indicated by the patch of grass glowing rather than shaking.
