Yes. Sonar uses sound waves and is not harmful. We encounter sound waves all the time in our every day life, simply by communicating with others and experiencing the world around us. The sound frequencies used in the app are above the level of normal adult human hearing and well within the range that is considered safe.
And because the sound frequencies used in the app are transferred via the air rather than applied directly to the body, the energy levels emitted are minimal and fall within the acceptable range highlighted in numerous publications and guidelines.