From <a href="http://www.blipsystems.com/indoor-sensor/" rel="nofollow">http://www.blipsystems.com/indoor-sensor/</a>:<p>> When a device passes the sensors, its non-personal unique ID, called a MAC address, is recorded, encrypted and time-stamped. By re-identifying the device from multiple sensors, travel times, average speeds, dwell times and movement patterns become available.<p>Aren't MAC addresses spoofed on most phones now?! I didn't expect a system like that to still be usable.