Trends in contemporary science education emphasise the benefits of out-of-school learning experiences to help schools link science with everyday life (Tho, Chan, & Yeung, 2015). With the help of state-of-the-art technology, mobile devices--particularly smartphones--have the ability to work as data-logging tools for students to perform scientific investigation (Tho & Yeung, 2014). In this study, the research aim was to develop a hands-on activity to explore simple harmonic motion (SHM) in a playground using a smartphone for secondary school physics (Form 4 in the Malaysia Education Curriculum, ages 16-17) or senior secondary physics (Year 11 in the Australian Curriculum, ages 16-17).