Hotmath is a lovely website with four games that focus on Algebraic skills. As they appear to be flash based, I don't think they will work on the iPads. That said, they do work on computers so they can be used in class.
The first game is Catch the Fly in which you give the frog the x and y coordinates so he can catch a fly. You see the fly moving around. Once it lands and is still, you type in the points and hit the button. The frog moves up on the fly, shoots a tongue out and grabs it.It is a great way for the student to become familiar with reading the coordinate plane.
I enjoyed the Algebra vs the Cockroaches game where you put in the value for y = to show the line with a zero slope and shoot your weapon to kill the cockroaches. I chose the rocket! If you wait a bit, you get more cockroaches running along the line.
Then there is Number Cop which is a challenge, even at normal speed. The idea is you choose a number and then click on the multiples that race towards you as you are the speeding cop car. This was quite fast and many of my students could easily get frustrated. I wish there was an easy level so a person can develop the skills to use the game.
The last one is Factoris which is a take off on Tetris and I could not figure out how to do it. I suspect its because I've never played Tetris so I had no idea how to play. I think if I took time, I would learn it. It looked like a multiplication game using factors to create a product.
For my classroom, I would assign Catch the Fly and Algebra vs the Cockroaches as part of the lesson but I'd use Number Cop and Factoris as free time games so they can play it if they choose too.