Think Google Analytics for brick and mortar stores, using in-store surveillance cameras:
"Prism's software can count people that come into a business, measure the length of the line at checkout, and produce static or animated visualizations showing how people moved around a store. It is designed so that it cannot identify or track individuals. One national wireless carrier is already using Prism's technology to generate heat maps of where visitors go in their showrooms, to compare the level of interest in different devices—valuable data to them and to the device makers."
I personally believe that data collected this way is more reliable than when using mobile phones to log and track people's behavior inside the stores.
