X Blox

X Blox is a nice app that uses manipulatives for various mathematical concepts.
It is divided into learn and play.  There are 5 chapters with 9 levels to learn to use the manipulatives. 
Chapter 1 covers expressions,  chapter 2 is on factors, chapter 3 is on multiple variables, chapter 4 is on equations while chapter 5 is on quadratic equations. Chapters 1 and 3 are very easy to figure out how to use while chapters 2, 4, and 5 are much harder to figure out but no matter which chapter you work, if you do not get the blocks set properly, it won't work right.  The lets learn section is set up so the student can become familiar with the various blocks and concepts for each chapter. 
Once the student has mastered the learn section, he or she can move on to the play section which has three options.  The first option is called the sandbox which appears to be where the student can work out problems that they have on a paper or just play around.  The second option is the X BLOX Express which is a timed game so people can create various expressions within a specific amount of time. Finally is the factor challenge which is timed and again the student creates the problem at the top.
I think this app could be used in Algebra I so as to help reinforce the foundation of Algebra and give students additional practice in basic algebraic concepts.  I need to get this installed on my ipads so my students can utilize the app as we go through the course.
The last think I like about this whole app is that it keeps track of scores and these can be sent to the teacher who can use the results as formative assessment.