Retailers also use your MAC address from your phone which is always being published unless you take precautions.
http://lifehacker.com/how-retail-stores-track-you-using-your...
http://lifehacker.com/how-retail-stores-track-you-using-your...
We used a Cisco Meraki router once for a client and rigged it up to know who was in the office (for fun, to be aware that it could be done). It'd be nice to know the iPhone/iPad scramble themselves if possible.
1. https://arstechnica.com/apple/2014/06/ios8-to-stymie-tracker...