Paired via Bluetooth with a companion web account or mobile app, they can display this data in graphs.
They range in price from around $100 up to several hundred for a smart-watch version.
Auckland health and fitness consultant Lee-Anne Wann has been wearing a Garmin Vivofit activity tracker since June last year, and her average daily steps climbed from 8000 to 18,000.
Ms Wann said the fitness tracker motivated her to be more active without creating an obsession.
"[Activity] makes a huge difference to the food you choose to eat, how you feel, your mood and how you look, and we under-estimate that."
Ms Wann said inactive people, particularly those in sedentary jobs, would be unaware how badly the lack of exercise was affecting their health.
She was shocked recently to discover after an all-day university lecture she had walked only 2000 steps. It corresponded with tiredness, irritability and a craving for junk food, Ms Wann said.
"It was a real eye-opener. When you have one of these on you actually make a concerted effort to move."
The average person walks about 3500 steps a day, but research shows that hitting 10,000 improves health.
Ms Wann competes with her friends and clients for best daily tallies, with one totalling 23,000 steps in one day.
Garmin regional sales representative Shannon Rea said he had lost 19kg since he joined the company and was given a Vivofit in May last year.
Mr Rea said the fitness trackers motivated people to lose weight and inspired better overall health through automatic and personal goal setting.
He said the Vivofit had been hugely popular since its launch in New Zealand last April and each day about 7000 were sold across Australasia.
Other fitness trackers on the market include the Garmin Vivosmart, Fitbit Flex, Fitbit Charge, TomTom GPS Sport Watches, Sony SmartBand, Polar Loop Activity Tracker, Jawbone UP24, and Nike FuelBand SE.
No rest for mum who's motivated to move every time she sees red
Ami Kelly (left) and Lee-Anne Wann wearing a Garmin Vivofit wristband, which collects exercise data of the wearer. Photo / Jason Oxenham
Ami Kelly is more active than ever thanks to a fitness tracker she says motivates her to keep moving.
The Auckland mother-of-two has been wearing a Garmin Vivofit for seven months and some days notches up more than 20,000 steps. Mrs Kelly, from the North Shore, already trains regularly at the gym but said the fitness tracker prompts her to move hourly if she has been inactive.
"It actually motivates me when the red line comes on. I never thought it would work but I actually get off my butt and go and do something like walk around the house."
The red bar on the display screen reminds Mrs Kelly she has been sitting down for a lengthy period.
That motivation was the biggest benefit, according to Mrs Kelly, who said knowing how many steps she had walked in a day, distance travelled and calories burned was interesting but not essential to remaining fit. "It's really positive re-enforcement. You get quite a sense of achievement."
Mrs Kelly, a self-confessed fitness junkie, colour co-ordinates the Vivofit wristbands with her clothing and keeps the sleek-fitting watch on day and night. She said her sister, who recently had a baby, had used a fitness tracker to get active again.
Some of the options
• Garmin Vivofit, $129 - Learns your activity level by assigning personalised daily steps, one year battery life, water resistant up to 50m.
• Sony SmartBand, $139 - Waterproof, wearable 24/7, vibrating alert, Bluetooth.
• Fitbit Flex, $159 - During the day, it tracks steps, distance, and calories burned. At night, it tracks your sleep quality and wakes you in the morning.
• TomTom GPS Sport from $199 - Track time, distance and pace on an extra-large, high resolution display, one button control, also tracks treadmills.
• Jawbone UP24, $179 - Real-time updates on your progress; new app displays movement and sleep details.
- Prices: JB Hi-Fi, Dick Smith
