Smartphones and tablets are go-to gadgets to count calories, document daily jogs, measure heart rates and record sleep patterns. Some applications now even analyse blood sugar levels, track fertility or monitor moods for signs of depression.
Inexpensive and easy to use, mobile medical apps are also booming business: more than 97,000 varieties are available. By 2017, the mobile industry tracker Research2Guidance predicts, the market will grow to $US26 billion ($A29.31 billion). By then, the company estimates, half the world's more than 3.4 billion smartphone users will have downloaded health apps.
The technology could revolutionise healthcare by encouraging consumers to be more involved in their own fitness and by making medical technology more ubiquitous, portable and cheap. Increasingly, it could bring high-tech help to populations with little access to physician care.
But not all apps deliver the medical miracles they promise. And most aren't subject to US federal laws that safeguard medical information. So consumers need to be wary.
"People who are using these health and fitness devices record a tremendous amount of truthful and very sensitive information about their bodies and behaviours with companies that they know very little about," says Heather Patterson, a post-doctoral scholar at New York University's Information Law Institute.
Consumers willingly log everything from diet to sexual activity to tap all the features an app offers, she says.
"They want to get accurate feedback about their sleep quality and the exercise they're getting and make a decision about that muffin they're thinking about eating." They may not realise how the companies that collect that information are using it or know whether it's stored securely, Patterson says.
"They trust the companies to keep their information secure, but it's potentially problematic because this is legally an unregulated space."
A study published in July found that many medical apps don't encrypt the sensitive or embarrassing data that consumers input about their health.
Apps frequently share that data with advertisers and other third parties without users' knowledge. Of the free apps reviewed in the study, fewer than half posted privacy policies, and only half of those that did described the apps' technical processes accurately.
"In most cases the apps captured personal data and transmitted it to third parties in a way that was not disclosed in the privacy policy," says Beth Givens, director of Privacy Rights Clearinghouse, the consumer advocacy organisation that conducted the study.
Often data was sent unencrypted, Givens says. One app shared users' locations and other personal information with 10 other companies within three seconds of being turned on.
Unwitting consumers may be opening themselves to insurance or employment discrimination, identity theft, or targeted advertising that references their personal struggles with infertility, depression or incontinence.
Paid apps in the study tended to pose lower risks to consumers' privacy because they rely less on advertising to make money.
Givens advised consumers to look for a privacy policy before downloading any app. If there isn't one, she said, they shouldn't use the app. Consumers also should limit the personal information they provide, and assume that any information they do share may be sent to the app developer, as well as third-party sites, data-mining companies and marketers, Givens says.
