If you don’t use it, you lose it. School breaks, during which students do not regularly participate in instruction, can therefore have negative consequences on learning. This is especially true for mathematics learning since skills build progressively on earlier materials. How can we bridge these gaps in formal instruction? The Keeping in School Shape (KiSS) program is a mobile, engaging, innovative, and cost-effective way of using technology to help students who have time off between related math courses stay fresh on prerequisite knowledge and skills. Founded on learning theory and designed on a model of behavioral change, the KiSS program embodies retrieval practice and nudges by sending students a daily multiple-choice review problem via text messaging over school break. After rating their confidence in solving the daily problem students receive feedback and a solution. This study explores measures of participation, accuracy, and confidence in an implementation of the KiSS program over winter break between two sequential introductory engineering courses at a large state university in the Southwest United States. Results indicate that careful attention should be paid to the construction of the first few days of the program, and that encouragement, additional resources for review and practice, and an increased breadth of problem difficulty may improve participation.