Tech: Fitness goes mobile

3.5 out of 4 stars

The good: It offers a simple, attractive design. Its pedometer tracks steps taken, calories burned, and a proprietary measurement of activity called Nike Fuel. The accompanying iOS app and Nike+ website offer great motivational tricks.

The bad: It's worthless to anyone who doesn't have a Nike+ product, and isn't always accurate. There's no way to measure distance for specific runs, so it isn't useful for athletes. It's also pricey for what it does.

The cost: $149.

The bottom line: It can be effective as a motivator for casual exercise, but its limitations will leave serious athletes disappointed.

4 out of 4 stars

The good: Small, light and easy to carry, it effortlessly tracks your basic daily activity level. It has a host of online analytical tools, it tracks sleep quality, and it boasts both Android and iOS mobile apps.

The cost: $99.95 to $132.99.

The bottom line: The Ultra extends Fitbit's already impressive personal fitness data measurement abilities. Already a high-tech pedometer, it now has an altimeter to record stairs climbed, too. It isn't as advanced as more expensive mobile fitness gadgets, but the tiny device is easy to wear all day long and fun to use.

3.5 out of 4 stars

The good: Extremely versatile and possessing the flexibility of Android, the MotoActv tracks workout stats through GPS and a pedometer, and even suggests energizing playlists. It also has Bluetooth.

The bad: This gadget costs as much as a modern smartphone and is made for serious exercise only. It works only with Motorola handsets.

The bottom line: It can tackle just about any fitness task -- such as tracking workouts via GPS -- and serves as a very tiny digital music player. But if you're looking for a simple tool to measure daily activity and provide holistic advice on how to shed pounds, it isn't for you.

3.5 out of 4 stars

The good: The iPod Nano costs less than before, is easier to navigate and includes more Nike+ fitness tracking capabilities. It's also still the best clip-on music player money can buy.

The bad: Many features have disappeared over the years, including video playback, camcorder, microphone, speaker, games. The touch-screen interface requires too much attention without delivering many practical benefits.

The cost: $129 to $189.95.