Where marketers once sought to influence consumer purchases through in-store coupons and other POS promotions, the proliferation of online retailers will force marketers to use other means to attract shoppers. So-called beacon technology that can detect shoppers’ smartphones nearby and initiate buying experiences with tailored ads has been around for a few years, and it’s expected to grow, to the tune of $25 billion by 2024. A look at typical beacon system, and how the technology is poised to change marketing over the next decade.