An Android-based eModule app has been designed and developed for science, technology, engineering, and mathematics (STEM) education. The eModule consists of: (1) an Android demonstration of echolocation; (2) a set of notes describing the functionality of the app, the basics of echolocation, and its application to advanced signal processing systems such as RADAR, LIDAR, and SONAR; (3) quizzes to test the concepts introduced by the demonstration and the notes; and (4) companion videos. The eModule is, therefore, a holistic teaching and learning app that can be used across various grade levels including K-12, undergraduate signals and systems, and graduate DSP education.The app, “Reflections”, provides students a means to determine distances to objects while allowing them the ability to manipulate signal envelopes, signal shapes, signal types, and frequency constraints. The intuitive graphical user interface, combined with notes, videos and quizzes, creates a rich educational environment to help educate users with the fundamental concepts of signals, systems, and digital signal processing. In addition to its role in STEM education, the app has potential use in low-visibility environments and for spatial acoustic analysis. Preliminary assessments strongly support the effectiveness of the eModule as an education tool signals and systems and DSP classes.