These badges use an infrared sensor to gather data about face-to-face interactions, a wireless radio to collect data regarding proximity to other badges and send it to a central computer, an accelerometer to track motion of the participant, and a microphone to monitor speech patterns. At the event, the data from the infrared sensors was wirelessly transmitted to a computer that crunched the numbers, producing a real-time visualization of the event’s social graph.

— Technology Review: Smart Badges Track Human Behavior