The only reason I can think of for owning a cell phone (other than for use in emergencies) would be to participate in a flash mob generated by Improv Everywhere. This is the first of their videos that I ever saw. The following paragraph is a description of the event from their website:
On a cold Saturday in New York City, the world’s largest train terminal came to a sudden halt. Over 200 Improv Everywhere Agents froze in place at the exact same second for five minutes in the Main Concourse of Grand Central Terminal. Over 500,000 people rush through Grand Central every day, but today, things slowed down just a bit as commuters and tourists alike stopped to notice what was happening around them.
If you want to learn more about this event, or about other Improv Everywhere activities, you can check out their website.
Enjoy your weekend!