This thesis is dedicated to the developing of an interactive mobile application that together with audio input device forms an excellent and easy way to perform a respiratory rehabilitation exercise. It is intended for users with respiratory disorders and diseases as well as for those who only want to improve their prolonged exhalation and learn some useful breathing techniques. Additionally, I have presented some of the key points on the importance of respiratory exercises, why and how should they be performed, and to whom they serve the most. Besides, I have also focused on the computer technology and highlighted some of the main study fields related to computer graphics, graphic user interfaces and input computer devices, which played a great role in developing my project. I have also presented Unity3D game engine platform as the main software environment in which the project was created. Finally, on the basis of standard evaluation methods and user test results, I reviewed the completed project and presented some further development possibilities of the application.