While in Denver last weekend, while waiting at a stoplight, I saw an empty detergent container very firmly attached to a street sign. It seemed not really random, but as if someone very intentionally affixed it and wanted it to stay there.

I thought at first that there might be some underground, mysterious meaning to it - something like the 'shoe trees', where people tie the laces of shoes together and fling them into the branches of trees, or over utility wires.

Then, I put it to the Google-machine and landed on fastcodesign.com, which contends that there IS a purpose for the bottle attached to the signpost. A high-tech purpose. Seriously.

The site claims:

"inexpensive plastic contraptions that, despite containing no electronics or electricity, act like sensors and connect to Wi-Fi devices like your smartphone. It’s something that “no one has been able to do before,” according to Vikram Iyer, a University of Washington doctoral student and coauthor of a paper on the research.

So how the hell does this dark magic work? The answer lies in three design details: the type of plastic they use, ambient Wi-Fi radio signals, and rudimentary mechanical gears and springs."

You can get more details here at fastcodesign.com.