If you got your pedometer via a kids' meal or a cereal box, don't count on it to tally steps accurately or for long. Dan Heil, Ph.D., an exercise physiologist and researcher at Montana Sate University, in Bozeman, found that pedometers that gauge movement with a flimsy mechanism called a hairspring and that cost less than $15 often wear out within six months. He also found that pedometers driven electronically or via a more substantial coiled spring, and which cost about $25, are considerably more accurate at counting steps. However, he warns, "distance, speed, and calories-burned measurements have a tendency to be inaccurate no matter how much a pedometer costs." So skip those kinds of features, which are found on the most expensive models.