Ever lie to your parents, even once, about where you were after school? It'll be tougher for today's teenagers, who may have to leave their smart phones behind if they don't want Mom and Dad following their every move. An increasing number of apps for mobile devices are utilizing GPS technology to help parents keep tabs on their kids. One research firm estimates that more than 70 million people across North America and Europe will be using such programs to track family members by 2016.

Skeptical? Some 20 million people have already downloaded Life360, a location app that allows family members to alert one another when they've arrived at various spots and to follow one another's movements with by-the-minute updates. Jessica Denay, a single mother in Los Angeles, uses Life360 to monitor her 12-year-old son Gabriel as he travels to school, basketball practice and her ex-husband's house. "I can't even describe how comforting it is," she says. "It's hard for moms to let go of our babies. This makes me feel better. I don't have to be hovering right there, but I know that he's safe."