In Pokémon Diamond, you can obtain similar items to revive fainted Pokémon:
* Reviver Seeds: You can find them in various locations, including some hidden in the grass, as rewards from trainers, and from the Rare Pokémon in the Grand Underground.
* Max Revive: This item fully revives a Pokémon and can be purchased from the Pokémon Mart in Veilstone City.
If you need to heal your fainted Pokémon in Diamond, you can also use Potions, Super Potions, Hyper Potions, or Max Potions.