This chapter discusses portability and flexibility afforded by mobile technology such as laptops and smartphones, which facilitate use across multiple contexts, providing the potential for experiential learning and increased levels of student engagement. The chapter shows how the co-incidence of the three factors: mobile learning, Realistic Mathematics Education (RME) and the Bridge21 model of 21st-Century (21C) Learning give rise to learning opportunities that optimize the potential of each component. The concept of using a Barbie Bungee to explore mathematics is not original, the loosely scaffolded, team-based and technology-mediated approach gives rise to an activity that is contextualized and realistic and is rich in promoting both generic 21C skills and mathematical content. All of these activities make use of the flexibility and engagement afforded by mobile technology some involve purpose-designed apps, and none of the activities would be feasible in a traditional classroom setting based upon a didactic, individualized, de-contextualized approach to teaching and learning and short class periods.