By completing certain tasks in the demo version, you can send certain items and Pokemon to the full version of Pokemon Sun & Moon when it launches via the Pokemon Link option in those games.

Bonus	How to unlock
Ash-Greninja	Finish an adventure.
Nugget	Clear the Pokemon Capture Challenge.
Star Piece	Defeat all of the Trainers at Ten-Carat Hill.
Stardust x3	Get rid of all the rocks in Mahalo Trail.