Osy Osmosis is a fun, educational game where you help Osy stay safe as she navigates through a very cool world collecting stars. The trick is to use osmosis to keep her in balance.
The game is not free ($1.99) but is very good, very fun, and educational. It was developed by researchers and educators and profits go towards creating other educational games.
It could be used as a great way to help teach osmosis in a fun way.