Fitness trackers are surging in popularity, but are they any good for you? And are they any good for the doctor who is treating you?

The devices, worn on the wrist, clipped to the belt or shoved into a pocket, measure your movements and, at the very least, promise to calculate how many calories you burned on your walk to work. Some offer considerably more, with myriad sensors measuring health indicators.

The fad went mainstream last year, when 48m devices were sold worldwide, according to research firm CCS Insight. Sales are expected to rise to 61m this year and 131m a year by 2019. And that does not include devices such as smartwatches, which can also include fitness-tracking features.

But can fitness trackers help health professionals keep tabs on their patients, or are they just a consumer gimmick?

Fitness trackers use an accelerometer, detecting motion and translating it into steps, distance and calories burned. Other sensors include heart rate, sweat, temperature, UV and skin conduction monitors, capable of measuring anything from body fat to blood oxygen level.

The efficacy of the units has been a subject of debate, however. Many believe they act simply as motivational aids rather than data-driven miracle cures. Researchers from the University of Wisconsin–Madison found that women given accelerometer-based trackers in a small study over a month increased their moderate physical activity by more than an hour a week.

Their accuracy has also been called into question, with market leader Fitbit embroiled in a lawsuit over heart rate data. Iowa State University researchers tested a group of accelerometer-based fitness trackers against a portable metabolic system and found the best fitness trackers, including Fitbits, were inaccurate by up to 15-18%.

For the NHS, consumer fitness trackers that are regulated under the “wellness” category, and not to the same standards as medical equipment, are a curio rather than a solution.

Beverley Bryant, director of digital technology for NHS England, said: “If a patient goes to their doctor and says ‘I have a fitness tracker’ and the doctor thinks it’s a good thing, in a conversation about weight loss for diabetes, then who’s to say that uploading their activity levels with their blood glucose could not be beneficial? But it needs to be on an individual level, rather than NHS-wide.”

But wearable technology that shares a lot in common with fitness trackers could form an important part of the future of the NHS, as limited resources lead to greater reliance on remote monitoring to maintain care.

Bryant said: “We’ve got trials with diabetics uploading the results of their home monitoring, which is looked over by GPs. It allows clinicians to spot, say, if someone has a peak of blood glucose on a Sunday linked to a big Sunday lunch and have a conversation around that.

“Being able to monitor their own condition and upload their readings is helpful for both patients and clinicians.”

Remote monitoring of medical devices is not new. University Hospital Southampton, for instance, remotely monitors more than 1,000 patients with implantable cardiac defibrillators to detect problems and deal with them as early as possible.

Some GPs, such as Piers Longhorn, a partner at the 10,500-patient Oaklands medical centre in Cheshire, would like to see wider use of monitoring. He said: “Patients have been able to share health data on their iPhones directly with my clinical system during a consultation for over a year. So far only one patient has done so. I had hoped it would be the end of transcribed blood pressure readings on bits of paper.”

Dr Mohammad al-Ubaydli, founder and chief executive of patient records system Patients Know Best, said: “Every patient hates medical devices. Consumer trackers are much more usable, but their data needs to be audited and treated with regard to what kind of device it comes from. Quantified-self logging can be useful in some situations as it’s additional data.”

Clinical home monitoring devices are clearly the future, with the digital health ecosystem expected to be worth £1.3bn in the UK alone, according to data from the government’s Office for Life Sciences. But on the hundreds of fitness trackers entering the market in 2016, the jury is still out.