Retailers already do this: https://www.washingtonpost.com/news/the-switch/wp/2013/10/19/how-stores-use-your-phones-wifi-to-track-your-shopping-habits/ https://

Retailers already do this: https://www.washingtonpost.com/news/the-switch/wp/2013/10/19/how-stores-use-your-phones-wifi-to-track-your-shopping-habits/ https://www.washingtonpost.com/news/the-switch/wp/2013/10/19...