1. Fitbit What it tracks: Steps, calories burned, mileage, movement intensity, sleep length and quality; input additional workouts and calorie consumption online Standout feature: Tracks sleep quality Cost: $99, fitbit.com [sidebar] This gadget gives instant feedback on step counts, calories burned, and daily mileage at the touch of a button, and even calculates the intensity of your movements, such as strolling throughout the day versus fast walking or running for a workout. It also detects more subtle movements like standing up versus sitting, for more accurate results.  Once connected to a computer and online, you have the option to input additional workouts and food logs to your profile, or check out the accomplishments of other Fitbit users. The pinky finger-size device can be worn anywhere and works even while you sleep (tester tip: Tuck the device fully inside the included wristband to prevent it from slipping off during the night). Once you wake you’ll have a complete assessment of time spent sleeping, including the length of time it took you to doze off and the number of times you woke up during the night—which can be surprising. 
  2. The Gruve What it tracks: Calories burned, intensity of activity, sedentary time; a 70-page workbook allows you to follow a 12-week program and detail your eating habits Standout feature: Vibrating reminder to move Cost: $199.95, including a 1-year Web membership for long-term tracking, muveinc.com This sleek calorie tracker was developed by James Levine, MD, PhD, the professor of medicine at the Mayo Clinic who coined the term NEAT for everyday activities that add up to a big calorie burn. (He’s also responsible for our favorite workstation, the treadmill-based standing desk.) A 1-week assessment determines daily activity goals; once you start the program, the small device, which clips onto your waistband, will light up—changing from red to orange to yellow to blue to green—as you accumulate activity. Fall into couch potato mode, and a gentle vibration cues you to get moving. (For our tester, it buzzed after about 45 minutes of inactivity.)  To check actual calories burned and the intensity of those calories, and to get tips on how to better reach your goals, just connect the device to your computer (PC and Mac compatible). [pagebreak]
  3. Philips DirectLife What it tracks: Steps, activity intensity, calories burned Standout feature: Wear anywhere, and recharge only every 3 weeks Cost: $99, with 4 months of personal Web coaching; $12.50/month thereafter, directlife.philips.com This tiny device (it measures about 1 inch by 1 inch) can be tucked in a pocket or bra, or attached to a belt or necklace and worn all day. In addition to getting a read on step-based activities (like walking or running), the device will pick up movement from exercises such as cycling and swimming (yes, it’s waterproof). After a week-long assessment, a 12-week activity program is created; plug the device into a computer to track hourly activity levels both present and past. For in-the-moment motivation, an arrangement of lights on the gadget reflects how near (or far) you are from hitting your exercise goal.
  4. Bodybugg What it tracks: Steps, physical activity, calories burned; an online food database to measure calorie consumption Standout feature: High-tech sensors measure motion, core body temperature, heat conductivity, and sweat rate for more accurate readings Cost: $280 to $350, including display watch and 6 months of Web service, 24hourfitness.com Made popular on The Biggest Loser, the Bodybugg straps onto your upper arm to track total energy expenditure, providing more than 90% accurate calorie read—based on an independent, published study. Our tester loved that this device measured her static activity—like lifting weights and washing dishes—and that the online tools helped her log food and provided exercise and healthy eating tips and motivation. Current models are smaller and PC and Mac compatible.