Why don't they link the iPod Nano to the iPhone?

I find it pretty frustrating that the iPod Nano still does not have any integration to the iPhone itself. iPod Nano is what you can describe a iPod on the wrist. However, it can only play music.

What if the iPod Nano can link to the iPhone and :

1. show you the latest SMS
2. control the music in your iPhone
3. allows you to make and answer phone calls through the iPod Nano and allows you to talk through an inbuilt mic within the iPod Nano

Pretty cool?