Chicago’s calling it “The Array of Things” AoT. Temperature, humidity, light, sound, carbon monoxide, nitrogen dioxide, motion, low-resolution infrared, cell phone signals, and foot traffic via Bluetooth are among the metrics being used to better understand the city and the interaction which occurs among its residents and visitors. It will be done with about 500 sensors installed cumulatively over a period of three years. The data, hardware and software will be open source, which is expected to promote transparency and invite independent developers to come up with their own applications. There will be no surveillance devices incorporated into the array.