Publishers have also taken notice. As part of my Codie Judge duties I just received access to Pearson's entry into the app world for math AlgebraPrep which is up for a Codie award this year. I'm looking forward to reviewing it.
In the meantime you can check out some of the apps that are now available. I did a simple Google search and came up with mostly links to test prep, drill and practice, and puzzle/game types. I'll do a little more research and and share about some apps that I find interesting and useful in my next blog entry.