[Employers could] monitor who is spending how long on coffee breaks or how often people are going for smoke.

Former triathlete Jeff Temple started wearing a fitness tracking device two years ago when his company gave it to him as an annual gift.

He could have chosen a branded jacket or a backpack. But, like 150 other employees at cloud computing company Appirio, he opted for the Jawbone tracker with membership of the associated in-house CloudFit programme in a bid to regain his fitness.

“I was very active and even completed an Ironman triathlon. Then I kind of burned out,” said the 33-year-old field marketing manager. “I took a couple of years off and got very sedentary, but the CloudFit programme re-energised me and got me back on the road.”

This sort of motivation is encouraging more companies to offer fitness trackers as a perk. After all, a healthy employee is a productive employee. Products from Fitbit, Jawbone, Nike and Samsung and others are presented to willing, and sometimes less-willing, employees in the name of fun, fitness and improved profits.

It works. For some. For others, having their employer track their every move is just a little disconcerting. What’s more, the technology isn't perfect and there are concerns about breaches of privacy considering all the data the fitness trackers collect.

Temple, however, is reaping the benefits. He now sets himself a lofty goal of 20,000 steps a day. Normally, he hits an impressive 15,000. Beyond measuring steps, Appirio’s programme, which switched to Fitbit from Jawbone at the request of its employees, also provides coaching and nutritional support, encourages employees to chat online about their achievements and runs regular competitions. The contests span global offices and bring employees from all levels and locations together in randomly selected teams to compete online, Temple said.

“I've noticed a motivational change in (my) behaviour... You notice when you drive to the grocery store, you think maybe I'll drive a little bit further away and get a couple of extra steps in,” he said.

The upside

The feel-good factor has made fitness trackers extremely popular, despite only 10% of owners using theirs every day, according to the latest survey by audit firm PriceWaterhouseCoopers.

“Corporate wellness programmes are well-funded, well-respected and well-liked, particularly in the United States, despite the lack of hard evidence on their effectiveness,” said Jonathan Collins, principal analyst for ABI Research. He estimates that around 13m trackers will be brought into corporate programmes in the US alone by 2018, compared with only around 200,000 in 2012.

Much of this is driven by the high cost to companies of health insurance in the US. “In the future when you get hired to work at a company they’ll say, ‘you're going to be enrolled in our wellness programme.’ You can opt out, but if you do, you're going to pay more for your health insurance,” said Dan Ledger, principal of the wearables and health practice at mobile and business consultants Endeavour Partners in Cambridge, Massachusetts, in the US.

For the time being, Appirio’s healthcare provider funds the company’s wellness programme, but it remains entirely optional for employees. There are no financial benefits for employees who opt in or penalties for those who opt out, yet more than half of the 1000 people at the company have joined.

“We have looked at healthcare premium incentives for employees, but the US is very different from other countries,” said Shannon Daly, Appirio’s vice president of HR Operations. “We are active in Europe, Japan and India. We don’t want to focus any benefit on just one country.”

As the popularity of fitness devices increases, prices fall and more companies can afford them. The latest Mi band by Chinese company Xiaomi costs $13 and monitors sleep, fitness, has an alarm and can even switch your mobile phone on and off, Ledger said. The Mi contains the same state-of-the-art components as $100 trackers from better-known brands, and has proved so popular in China that demand has exceeded supply.

Not fail-proof

Historically, the problem of turning body movement into a measurable number of steps has proved an imperfect science.

A few months ago, when Rachel Metz of MIT Technology Review compared three fitness bands from leading companies simultaneously, she discovered a difference of more than 40% between the highest and lowest score. “On the same day, the FuelBand SE said I had taken 9,725 steps, the Force counted 11,981 steps, and the Up 24 logged 6,785,” she wrote. “Over weeks and months, such differences would really add up.”

Results can also be rigged. Consider the “cheat-o-matic”. Invented by Andy Frey, chief technical strategist at Arizona-based Meltmedia, while he recovered from an Achilles tendon injury that prevented him from participating in a corporate walking contest. Using little more than scrap wood, a programmable electric motor and an elastic band, he built the device, attached his Fitbit and racked up more than 145,000 steps, or 78 miles, in less than a day spent mostly sitting at his desk.

Too much information

Manufacturers recognise their devices can't yet measure every exercise perfectly, especially if the action can't be broken down into steps, so they allow users to complete online records with some of their own details. Owners can, for instance, include data on activities such as weight-training, yoga or even what they get up to in bed.

That's fine if your activity data is kept private. But what happens when your exploits are shared with your friends, your boss or on the internet?

In 2011, techie and blogger Andy Baio discovered a simple Google search could expose details of Fitbit users' sex lives. The company quickly removed sexual activity as a tracking option and made it easier for users to choose which of their activities to share. This lapse provided a salutary lesson for leading manufacturers, which now emphasise their privacy policies.

“We have always been committed to protecting consumer privacy and keeping data safe,” a Fitbit representative told BBC Capital. “We have spent the last several months updating our privacy policy to clarify our practices and provide transparency for our customers.”

However, concerns over possible data breaches remain. Trackers constantly transmit data that can be intercepted. Often it’s harmless, like the number of steps an individual has taken. But, the latest wearable devices are beginning to collect more detailed health information that, in the wrong hands, could be misused, according to Candid Wueest, Symantec’s principal threat researcher.

“Going into a meeting with a competing company, it could be very interesting to know their executives’ pulse rates because they can act as a kind of lie detector or at least a stress indicator,” said Wueest. “I would certainly ask members of the board if they should be using those wearables or not.”

Breach of privacy

In July, Symantec published a report on activity trackers entitled: “How safe is your quantified self?” which found anybody wearing a device could be tracked using a simple scanner made by researchers with a minicomputer, a Bluetooth adaptor, a battery pack and an SD card.

“An employer could buy devices like these and place them at strategic points such as the door to the smoking room or to the cafeteria. Then they’d be able to monitor who is spending how long on coffee breaks or how often people are going for smoke,” explained Wueest, one of the report’s authors.

He said 52% of applications linked to trackers have no privacy policy meaning the companies are free to sell users’ data. “An employer could get these statistics de-anonymised so they could see who are the lazy employees.”

Data from smartphones and fitness trackers can already be very revealing, showed researchers from Fordham University's Wireless Sensor Data Mining Lab while developing a free Android activity app called Actitracker, released in 2013.

“What they discovered is simply by looking at the data they can find out with pretty good accuracy what your gender is, whether you're tall or short, whether you're heavy or you're light, but what's really intriguing is you can be 100% identified by simply your gait,” CIA Chief Technical Officer Gus Hunt explained at a conference in March 2013. Hunt has since retired from the CIA.

Still, for the most part, the benefits of fitness trackers outweigh possible threats, Wueest said.

Temple plans to continue using his tracker, adding he is in full control over what he shares with his employer. He doesn't reveal sleep data, for example. Neither is he forced to participate in the company CloudFit scheme. “If I have a week when I don't want to participate, I am free to take off the tracker and jump back in when I am ready.”

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