Make Your Own Soda With Soda Stream
These type of machines have actually been around for years.  My friend had one when I was a kid and we used to pester his mother to let us have more soda.  I don't remember what it was called, but essentially it was the same idea, you were shooting Co2 into regular tap water and adding syrup to flavor it.  So what is the benefit of this thing, it is still soda, ya know?