Kites have been used in China for nearly 3000 years—as entertainment, but also to estimate distances, measure wind speed, and send coded messages in wartime. More recently, they've been put to use to help monitor the polluted air in Beijing.
As we wrote last July, two U.S. graduate students created a project called FLOAT that teaches Beijing residents how to build simple pollution sensors into kites. The sensors are connected to LED lights; the lights glow hot pink if levels of pollutants are very high, and change color as the air gets cleaner. The pollutant levels are also recorded and stored, and send wirelessly to a database.
For Chinese citizens, who have often lacked accurate data about air pollution, it's a way to circumvent government reports. (This week, as the air quality became so terrible that it actually broke the WHO scale for the worst-case scenario, no one needed kites to know that it wasn't safe to go outside).
New York-based filmmaker Joshua Frank created this short video about the project.