text: Microsoft has just launched its first wearable health gadget, the Band, in the US ahead of its global launch.
  Similar products from Samsung and Google are already on the market and early next year the much-hyped Watch from Apple will go on sale.
  Millions of us are going to be having our most intimate bodily functions monitored by these gadgets, creating more health data than has ever existed before.
  Why do these machines help us stay fit and more importantly what happens to all that information we are generating and sharing?
  Before the giants of the tech world realised that wearable, health-focused gadgets were the new big thing the market was already thriving.
  In March the European Commission published its green paper on mobile health, which contained some mind-boggling statistics.
  It suggests that 97,000 apps are on sale in the mobile health sector, which includes tracking apps but also apps that help patients make appointments and keep track of medication.
  It predicts that by 2017 more than 1.5 billion people around the world will be using these apps, generating total revenues of Â£14.5bn ($23bn).
  In the EU alone it is estimated that these apps and gadgets could reduce health costs by Â£77.5bn (99bn euros).
  Most of the growth has come from start-ups that saw the potential early and now face a competitive onslaught from the big technology companies.
  Five years ago French firm Withings launched its wireless scales - the device feeds data back to you, by plotting a graph of your weight over time.
  "It started with the scales because we thought that was the one dimension that would make sense for people to track," Julien De Preaumont, chief marketing officer at Withings, says.
  "The first rule of data is to make people aware of their health to make them realise how their weight is evolving.
  "The curve reveals the impact of life changes, it will show how a divorce, a diet or a new job will affect your weight."
  After the scales took off, Withings launched wearable gadgets that track your movement, heart rate, blood pressure and sleep.
  The company maintains that the data it collects belongs to the user only.
  But it has published reports revealing the most obese cities in France and the US, as well as another study showing sleep patterns across Europe.
  Withings says this does not compromise the privacy of the individual user's data because it is aggregated and anonymised.
  While Withings has grown to be a global business, US firm Fitbit has also seen its business thrive beyond its borders.
  Founded in 2007 Fitbit offers wireless scales, wearable devices that monitor movement, heart rate, sleep and blood pressure, and is evangelical about the motivating power of targets and data on our health.
  Fitbit also offers companies its gadgets and software for corporate use.
  Its "corporate wellness" scheme started in the US and companies can use the scheme to get a rebate on their taxes.
  Clients so far include blue-chip multinationals such as BP and Time Warner.
  Employees can sign up and different divisions can compete against each other over the number of steps taken or stairs climbed.
  "The key is to make the product sticky," says Gareth Jones from Fitbit, and the key to that is gamification.
  "Our software incorporates challenges like daily showdowns and weekend warriors which motivate people and keep them coming back."
  But should employees be worried about sharing their every movement, 24 hours a day with a corporate scheme?
  "We don't have data about this, it's very much a choice of the individual as to whether they sign in for the programme. We see the result of that as purely the people who agree to participate and the people who don't," says Mr Jones.
  "We might share with the corporate administrator information that 50 people have been invited and 45 have said yes. How the company uses that information is up to the company."
  The potential of all the data that is now being collected is huge, both for business and for public health bodies.
  Imagine going to the doctor and being able to show them how much exercise you do, how much sleep you get and your blood pressure for the last year.
  While the insurance industry is using mobile applications for arranging appointments and giving health information, they are yet to fully embrace the use of wearable devices and the data they collect, though it is a development that could completely change their business as many research papers suggest.
  Can big data really revolutionise our world? We explore how the explosion of information and analysis will impact our lives and our privacy.
  Power of big data
  Meanwhile the use of the data for medical research is also a long way off.
  Professor John Newton from Public Health England would like to see a more joined-up approach.
  "We've got the world of apps, a huge investment from the technology companies, but the healthcare sector hasn't made the link," he says.
  "If you were able to make the link between a hospital service like a diabetic clinic with a patient's mobile phone data, they could tell immediately whether that person's diabetes was going out of control."
  His message is clear: "Put the data into the hands of the people who can use it to make a difference."
  Like all the new data that is being recorded and analysed the possibilities are massive but the ethical and privacy issues surrounding our personal information will not go away quickly.
target: Gadgets that track your steps, sleeping and heart rate could help us live longer and cut national healthcare costs by billions - or so we are told.