For indoor locations where there is no line-of-sight to GPS, there are other solutions, and this is where imminent progress is being made. There are WiFi networks (where even having WiFi enabled is enough know that ‘you are here’ or at least that your phone is ‘here’), Bluetooth Low Energy (per most smartphones), and now iBeacon and similar technologies. iBeacon, etc. is essentially an RFID technology where there would be a beacon on each grocery store aisle that could track customers and deliver coupons or other notifications. However, Bluetooth would need to be enabled which most smartphone keep off. In all of the industry promoted excitement over proximity marketing with real-time couponing, one cannot help but notice that truly revolutionary progress, for example auto-checkout per item-level RFID tags or some other mechanism remains a hard, expensive, and unsolved problem. What about remote hover cam item selection and personalized drone delivery?
For outdoor retail locations, GPS is still a good solution as it can locate a person within a meter per satellite pings. GPS resolution is already available in centimeter resolution for professionals (at $1000 and reportedly now at $500). This cost/performance curve could continue to ratchet down and centimeter-level GPS resolution could harken exciting new classes of location-based technologies, for example medical applications that require sub-body level detail.