Automatic downloads - for specific devices only...

I'd like to see automatic downloads for specific devices only. For example my household all uses the same Apple ID for purchases, but when I download a song, app or book, they won't want it on their devices but I want it on mine.

I've an iPad 3 and an iPhone 4S. It'd be great if I could set automatic downloads on my iPad 3 or 4S to go to each other.

I hope Apple introduces this as a feature in iOS 6. It's not as fun doing it manually.