In our pursue to study effective real-time feedback in Technology Enhanced Learning, we developed the Presentation Trainer, a tool designed to support the practice of nonverbal communication skills for public speaking. The tool tracks the user's voice and body to analyze her performance, and selects the type of real-time feedback to be presented. This paper describes an empirical study where we tested the effects of the Presentation Trainer's feedback on learners who used the tool while practicing for an elevator-pitch. Results from this study reveal that the feedback has a significant effect on the learners' motivation, confidence, self-awareness, and performance.