Artist Simon Weckert borrowed phones from friends and rental companies until he had acquired 99 devices, which he piled into a little red wagon. He then walked up and down a given street, mostly at random, towing his smartphone-packed wagon behind him. Inevitably, Weckert says his wagon created a long red line in the app, indicating that traffic had slowed to a crawl—even though there wasn't any traffic at all. He had effectively tricked the system into thinking a series of large buses were crawling back and forth.
You can watch the video here: https://www.youtube.com/watch?v=k5eL_al_m7Q