Your Phone Knows Where You Sleep

Your cell phone knows more than it lets on. Most can tell where they are, for starters, and how close other phones are. Since most of us tote them everywhere, our phones could track or analyze movement patterns for huge populations. “This is obviously sort of useful,” says MIT researcher Sandy Pentland, a pioneer in this new field of “reality mining.”

The information goes beyond movement. Phone microphones can monitor your tone of voice, and the iPhone’s accelerometer can tell whether you’re sitting or walking. Pentland sees real-world applications, but he knows it sounds scary. “It could stop SARS, but there’s a big trade-off,” he says. We need “a new deal for privacy,” he says, without sticking our heads in the sand. (More privacy stories.)