Classic fitness advice says kids need an hour of vigorous activity every  day. In theory, that makes sense. In real life, it can be tough figuring out whether your child's gotten 5, 10 or 200 minutes of activity in a day. When they're in school, you're not there to see what they're doing. And even when they're at home playing in the backyard or jumping around in the basement, they're not actually in constant motion – kids' play and even most kids' games (from kickball to freeze tag to soccer) involve lots of starts and stops.

But a cheap piece of technology could help. Plenty of kids will wear a pedometer. And a new study of 1,613 kids ages 6 to 19 says that by checking the number on the screen, you can estimate their activity level. Researchers from Canada's Children's Hospital of Eastern Ontario Research Institute determined that kids who get 12,000 steps a day are hitting the 60-minute goal. "Step counts are something that children and teens can easily monitor themselves and use to work toward personal health goals," says lead author Rachel Colley, Ph.D.

You could spend $25 to $99 (no, that's not a mis-print!) for a special kid's pedometer. But don't do it. Pedometers get dropped, lost, left in pants pockets and run through the washer and dryer. A cheaper model makes more sense; you'll find pedometers that cost as little as $5 in local discount stores.

But don't just hand one to your kid or teen. Get one for yourself (experts recommend that adults work up to 10,000 steps daily, roughly 5 miles) and for other family members and start a friendly competition. The more you move, the more your child will, too. In one fascinating French study of 286 families, researchers found that parents who logged the most steps had kids who did, too. Or help your child log her steps on fun Web sites like PE Central's Log It.

Plenty of kids in the Philadelphia area already wearing pedometers. In West Philadelphia, a program called Dance for Health brought University of Pennsylvania nursing program professors and students out to Sayre High School for weekly dance classes with kids and adults ages 5 to 91. Participants wore pedometers – and found that they got twice as many steps on dance days.