MACH, My Automated Conversation coacH, is a system for people to practice social interactions in face-to-face scenarios. MACH consists of a 3D character that can "see," "hear," and make its own "decisions" in real time. The system was validated in the context of job interviews with 90 MIT undergraduate students. Students who interacted with MACH demonstrated significant performance improvement compared to the students in the control group. We are currently expanding this technology to open up new possibilities in behavioral health (e.g., treating people with Asperger syndrome, social phobia, PTSD) as well as designing new interaction paradigms in human-computer interaction and robotics.