Tennis coaching costs $80-150/hour but a coach cannot see your stroke in slow motion during the lesson

You take a tennis lesson for $100/hour. The coach feeds you 200 balls. They say 'your backhand follow-through is too short.' You try to adjust. They say 'better but your wrist is still opening.' You cannot see what your wrist is doing — it happens in 200 milliseconds. The coach can see it in real time (years of trained observation) but you cannot feel the difference between 'open' and 'closed' wrist at contact. You leave the lesson with verbal instructions but no visual reference. Two days later, you cannot remember exactly what the coach corrected. So what? Tennis technique happens at 50-100mph with contact lasting 4 milliseconds. The difference between a good shot and a bad shot is 5-10 degrees of racket angle or 2-3 inches of contact point. This is too fast for human perception during play. Slow-motion video analysis exists (SwingVision, Playsight) but: SwingVision costs $15/month and requires an iPhone mounted on the fence (awkward setup), Playsight is installed on $50K+ smart courts that public court players cannot access. No tool gives instant slow-motion replay during a lesson that both the coach and student can review in real time. Why does this persist? The technology exists (any iPhone can shoot 240fps slow-motion). The missing piece is integration into the lesson workflow: automatic capture of every shot, instant replay accessible to coach and student, and AI annotation showing racket angle, contact point, and body position. SwingVision does some of this but requires setup time that eats into the $100/hour lesson. Coaches resist technology during lessons because it interrupts flow. The result: lessons remain verbal and experiential, not visual and data-driven.