Real time tracking of urban air pollution

Here's the really cool thing:

"Edwards and his colleague Kirk Smith altered commercial smoke detectors to act as particle monitors in the experiment, essentially creating for about $150 what previously cost as much as $6,000. The small, lightweight sensors record information continuously, providing a wealth of data."

Now, how much did those tests at Madison Park cost last year? Understandablely, they were donated, but imagine the possibilities with this!!!