I stumbled across this lite version of Dragon Box app and finally got around to trying it last night. I downloaded it because it markets itself as an algebra app. The idea is that as you work your way through various levels you feed the dragon and watch him grow and each level has a specific algebraic lesson associated with it.
I began by exploring chapter one, lesson one. I was wondering about the algebra part because I was just touching swirly green masses to get rid of them. This lead to matching opposite colored items and putting one on the other side. Not too long afterwards, I began working with the letter C. I soon discovered they have the person begin learning the process with nonmathematical representations before introducing algebraic representations. By the time this happens the student is ready to use algebra and would be comfortable with it. this app only has the first chapter and it really gives you an idea of how it works.
Dragon box comes in two versions, the 5 + for younger children and the 12+ for older students. Its a bit more expensive at $7.99 but it appears to be quite good. I am seriously thinking of buying the full version so I can see the full package but based on the information it gave at the end, it looks good and goes quite far in teaching algebra.