Cashierless checkout lets shoppers take what they want and leave, with payment handled automatically. It depends on the store recognizing who is present and charging the right person without a till.
The longer version
Cashierless checkout removes the till line. A shopper picks items and walks out, and the store settles the payment in the background. This just walk out style of retail is a category, not a single product. The hard part is not the charging, it is knowing with confidence who to charge and for what.
Recognizing the shopper is the foundation. If the store can identify which enrolled person is present and, when needed, which one is nearest a fixture, it can attribute a basket and complete payment through a server rather than at a counter.
Presence based recognition provides that foundation without relying on cameras alone. A short range signal can confirm who is in the store and resolve the nearest match, and the transaction routes server side, so the walk out stays simple and the charge still waits on the shopper's terms.
The Parousya method
Cashierless checkout is a natural application of the Parousya method. Presence identifies the shopper and server routing settles the basket, so a store can charge the right person without a till and without a direct device connection.