Sure, there are numerous adapters that plug into the iPod's dock connector to give you wireless music, but they are clunky, they come off easily, can't use them with your case and you have to charge them separately!
So, here is my way to add "native" internal Bluetooth support to your 4G iPod. The same method may be used with other iPod versions, I leave that up to you.
Check it out at Instructables.