Question about images PPI: should I care?

Hi guys.

I am trying to finalize my first IOS game (SpaceCommand) and I am wondering how to setup all my images:

I read on some site the following info about images

The iOS platform has these characteristics:
iPad: 1024x768px, 132 ppi
iPhone/iPod Touch: 320x480px, 163 ppi
iPhone 4: 960x640px, 326 ppi

Do I really need to worry a out ppi when it comes to digital image or these numbers are only for print media?

Sorry for maybe a stupid question!

Thanks

Mo [import]uid: 100814 topic_id: 29100 reply_id: 329100[/import]