Silicon Valley Nannies Are Phone Police for Kids

Making sure kids aren't spending time in front of screens is serious business.

The nanny spotters, the nanny spies,” said Ms. Perkins, the UrbanSitter C.E.O. “They’re self-appointed, but at least every day there’s a post in one of the forums.”

The posts follow a pattern: A parent will take a photo of a child accompanied by an adult who is perceived to be not paying enough attention, upload it to one of the private social networks like San Francisco’s Main Street Mamas, home to thousands of members, and ask: “Is this your nanny?”