Amazon Go's ("just walk out") self checkout gives you an elapsed time on your receipt. There was one next door to my old pre-pandemic office. My coworkers and I would complete to see who could get in and out the fastest. My record was 6 seconds buying a single bottled tea.
Honestly "track this person's movements and figure out what they picked up using this huge amount of sensor and camera data" should be a pretty good ML use case, but Amazon doesn't really have the right technical talent to make that work.
Was it really AI powered? I've never used one (we've not had them in the UK) so I'm genuinely curious. I heard it just had chips in every product, so when you leave the shop through a gate, everything you bought got scanned, and you were charged automatically. But in my description there is no AI in the modern sense of pattern recognition based on vast training data.