Lately, physical activity trackers are everywhere. Trackers are the chunky-looking bracelets worn by both men and women who have decided to make inroads on better fitness and diet.

While the devices might appear to be faddish, they are truly useful. They can turn an unappetizing poor-weather, lonely walk into a documented physical victory that friends and family want to know about, particularly among the friends who mutually share tracker results.

FitBit and Striiv are two brands that are already very popular. They will face added competition from Jawbone’s UP3 later in 2014 and from Apple Watch in the spring of 2015. Except for Apple, trackers are priced at about $100 to $200.

Most activity trackers measure the wearer’s daily “steps” and some can distinguish how vigorously the person is walking or running by using a three-axis accelerometer. Some measure your resting heart rate and time spent sleeping.  Trackers which have an altimeter can also detect and record stair climbing.

Users download their accumulated tracker data into a dashboard system resident on a tablet, laptop, smartphone, or smart watch. Users can enter non-step activity (e.g. felling trees, painting walls) to which the dashboard helps assign a calorie burn.  The dashboard lines up the results in graphic form, and manages sharing of result categories among users who have a compatible device and who have agreed in advance to share.

Some trackers encourage users to post the food they consume. The dashboards offer a robust database of raw, prepared, and take-out food items with associated calories, protein, fat, fiber and so on.  This is very helpful to those trying to loose weight, because careless eating can quickly undermine the shedding of calories through exercise.  For example, one Snickers bar can add 250 calories – about an eighth of the recommended daily calorie intake.  It takes a reduction of 2.5 typical days-worth of calories to lose one pound.  The dashboard highlights the balance between calories shed (via exercise or “sitting around”) and calories consumed. This graphic intake and exercise data encourages wise choice in meals.

Disparities in the tracked results can give out-performers a small thrill and can motivate laggards to up their game. Progress is usually gauged in weekly totals and 10,000 steps per day (about 4 miles) is the advertised goal for FitBit users, but 10,000 steps (1.25 hours at a brisk pace) is about triple the minimum aerobic workout adults need to maintain fitness since the CDC recommends 2.5 hours per week of moderate aerobic activity (brisk walking) plus muscle strengthening on 2 or more days a week.

The CDC says children need 60 minutes or more of aerobic activity per day, plus bone and muscle strengthening activities. Trackers don’t yet address muscle and bone strengthening, and it’s unclear how they could.  The food tracking component is especially useful for those trying to shed weight.  It seems activity trackers make inroads on obesity without preachy nagging from health advocates.

Trackers could be a helpful device to encourage and document children’s aerobic exercise since they track 24-hours per day – not just during assigned “laps” at school. That may improve the crude self-reporting on children’s disappointing activity levels. Trackers could help with aerobic exercise even for children who are disinclined toward team sports.

Alan Daley is a retired businessman who writes for The American Consumer Institute Center for Citizen Research