Pokemon Diamond UnlockablesUnlock Pal Park 
Pal Park will be on route 221 when you get the National Dex 
Unlockable  How to Unlock  
Pal Park  Get the national dex  

Upgrade Trainer Card 
Your trainer card when you begin the game is colored red. When you complete certain tasks,
stars are added onto your card as a sort of prestigious recognition for your efforts. In
the same way as in the previous generation of Pokemon, these stars will be accompanied by
the change of your card's color. They are typically obtained in order. 
Unlockable  How to Unlock  
Blue Trainer Card (One Star)  Beat the Elite Four  
Bronze Trainer Card (Two Stars)  Defeat all of the Master Rank Contests  
Silver Trainer Card (Three Stars)  Complete the Underground Flag minigame with friends  
Gold Trainer Card (Four Stars)  Capture 482 different Pokemon  
Black Trainer Card (Five Stars)  Win 100 times in a row at the Battle Tower  

Get the National Dex 
Unlockable  How to Unlock  
National Dex  Complete your Sinnoh Pokedex by seeing all 150 Sinnoh region Pokemon, go to
Prof. Rowan's lab and talk to him. Prof Oak will dash in and upgrade it.  

Pokemon Diamond SecretsHatch Egg Faster 
If you are trying to hatch an egg and have a Pokemon with the Magma Armor or Flame Body
ability in your party, then it will cut the hatch time in half