I've worked with a major retailer on similar backend systems and can echo the post above - all of them are running these systems and they almost never discuss the specifics (until someone like Walmart sues Everseen and we get a glimpse behind the curtain from the court documents).

If you go to an org's website offering these tools (eg, Everseen mentioned above, RetailNext, etc), they don't directly advertise the full breadth of their capabilities until you have them in a room for a sales pitch. They can combine multiple data streams such that an individual can be traced throughout the store via cameras, wifi, and bluetooth, which gives the retailer an opportunity to sell that information. Did a customer pause in front of the corn chips but then decide not to buy? Print them out a Frito-Lay coupon at checkout and see if you can't get them next time, and Frito-Lay will pay you to do that.