The first game that looks good for my high schoolers is Slope Intercept Surround which has students identify the m and b for two lines that surround the colored area. In essence, the graph represents the answer for two inequalities.
However the way the game is set up, you identify the two lines that border the colored area. when you click on the first slope, you are given a choice of four possible slopes and it is your job to select the correct one. Then you move to finding the intercept for the first line.
The process is repeated for the other line. Once the student has both lines correct, they move on to the next graph. As far as I can tell, the lines all match up with the type of graph you see to the right.
The second game is transformation golf.
This game requires students to identify the type or types of transformations needed to move the white circle to where the black circle is located.
The app moves the white circle up two. I'd choose translation again, right, one saying move it to the right one space. I'm done because the white circle has met the black circle.
Finally, Hooda Math has certain math manipulatives that can be used on the iPad. Its got Base Ten Blocks, Algebra Balance Equations, Algebra Tiles, Number Line Addition and A Hundreds Chart.