Academic oral presentations (AOPs) are crucial for students, especially those for whom English is a foreign language (EFL). AOPs allow students to share ideas, engage in academic discussions, and showcase their research. However, many struggle with integrating verbal, nonverbal, and visual elements seamlessly. Often, presentations become monotonous recitations or readings from slides, lacking engagement and dynamism. Inconsistencies between what’s spoken, how it’s delivered, and the accompanying visuals can also undermine credibility. Moreover, language barriers can further hinder EFL students' presentations. Researchers have developed Trinity, a mobile-centric system to address these challenges. Trinity offers on-the-fly guidance, synchronizing multiple communication channels for a more compelling presentation. It works in two phases: Preprocessing and Presentation. In the Preprocessing phase, using a PC, presenters upload their script into a PowerPoint add-in. Trinity, leveraging the power of GPT-4, refines the script for clarity and fluency. It also suggests integrated delivery prompts, covering verbal cues like vocal pitch and speech rate, nonverbal cues such as gestures and posture, and visual cues related to slide content and design. Presenters can customize these prompts based on their individual needs. After reviewing and adjusting the enhanced script, presenters optimize their slides according to the prompts and upload everything to the Trinity mobile app. During the Presentation phase, the app acts as a smart prompter. It displays the script with integrated verbal and nonverbal prompts. The presenter can use their smartphone to remotely control slides and visual cues, facilitating seamless transitions and enhancing audience engagement. Dual progress bars help manage speech pace, while underlining in the script guides the presenter to maintain an ideal tempo. Emojis are used to signal suggested modulations in delivery, making prompts intuitive and easy to grasp. To aid pronunciation, Trinity uses phonics to segment unfamiliar and polysyllabic words, making them easier to articulate. A user study comparing Trinity with standard presentation tools like IntelliPrompter and Office Remote showed significant improvements in AOP delivery. Presenters using Trinity received higher ratings from the audience for eye contact, facial expressions, gestures, vocal variety, and slide effectiveness. They also reported feeling more confident and engaged. However, the study also highlighted the importance of system robustness, as technical glitches could erode trust and increase cognitive load. Some presenters also noted that they relied less on the system when presenting their own work, indicating a preference for improvisation with familiar content. Trinity represents a promising direction for presentation support tools. It exemplifies the potential of AI-powered systems to enhance communication skills, particularly for EFL students. Future development could focus on improving hardware support, adapting LLMs to personal contexts, and enhancing system stability. Integrating Trinity into a comprehensive presentation ecosystem, with tools for preparation and post-presentation reflection, could further amplify its impact on learning and communication effectiveness.