Here's how it works; students sign-up on Study Boost and link their favorite IM service or SMS (mobile number) to their Study Boost accounts. Then students create batches of questions or find batches of questions made by others. After creating and or selecting batches of questions students "activate" those questions. Activating a batch of questions means that those questions will be sent via IM or SMS at intervals specified by the student. Students answer the questions and get feedback via IM or SMS.
Study Boost could be a good service for students to use to study on the go. Using Study Boost students traveling for club or sports activities need to only take their mobile devices with them study. As a teacher you can register and submit batches of questions that your students can study. Or students can create their own sets of questions to study.