Nudge is a free iPad and Android app that provides students with interactive, on-demand algebra tutorials. The free app provides students with practice problems that they attempt to solve on their iPads or Android devices. When they get stuck on a problem students can ask for hint or for a demonstration of how to solve the problem. In addition to showing students hints and demonstrations, Nudge will show them where they made their mistakes in solving a problem.
Learn more about Nudge in the video below.
Applications for Education
Nudge could be a good app for students who are motivated to practice algebra outside of the assignments that you give to them. Unfortunately, without becoming a Nudge partner, there doesn't appear to be a way for teachers to track students' practice activities.