The latest versions aim to use the phone as a DIY tool, taking readings to identify and monitor potentially life-threatening problems.
According to New Zealand experts, health apps have the potential to make healthcare more accessible and equitable.
"Such characteristics provide significant potential to assist in disease prevention strategies and supporting sustained change in lifestyle behaviours," they wrote in a report earlier this year.
However, they warn the huge number of apps offers too much selection and room for error.
From measuring heart rate to checking suspect moles, can an app really help to improve your health? We ask the experts ...
Skin cancer
Doctor Mole
$7.49, iPhone, Android and Windows
Doctor Mole is one of several apps that work in a similar way, claiming to be able to detect malignant melanoma, the most dangerous type of skin cancer.
Use your smartphone to take a picture of a suspect mole, and the app instantly analyses it for three key indicators - asymmetry, border outline and colour. It then gives a colour-coded 'risk' level for each characteristic. It can store images so it can compare next time you scan the mole. It also reminds you, via a message on your phone, when to check it again.
Expert verdict: "Most of these skin cancer apps have to be considered unreliable," says John Hawk, emeritus professor of dermatology at King's College London.
"They are very likely to miss moles that are a malignant melanoma, or highlight ones that are not.
"They can get it wrong both ways and that represents a huge risk to the patient.
"Looking at a picture of a mole is not enough to make a diagnosis. A doctor also needs to find out what changes have occurred in the mole."
Sleep apnoea
Sleep Assess
Free, for iPhone and iPad
Snoring can be a sign of obstructive sleep apnoea - when the walls of the throat relax and narrow too much in sleep.
It causes a complete collapse that shuts off breathing for ten or more seconds.
Air vibrates against the soft tissue that stands in its way, causing the characteristic "rasping" sound snorers make.
Left untreated, sleep apnoea can cause accidents, as sufferers are drowsy in the day, and raise the risk of high blood pressure and heart attacks, because lack of oxygen repeatedly disrupts sleep.
Sleep Assess works by recording snoring and comparing it with other recordings of diagnosed sleep apnoea sufferers.
Expert Verdict: Professor Jim Horne, former head of the Sleep Research Centre at Loughborough University, says: "Snoring by itself, apart from being a nuisance to a partner, may not be indicative of a sleep-related breathing disorder, unless the upper airway is really obstructed.
"Maybe the partner should use the phone's camera to film a video of the snorer's face during a snore and show it to their GP - it might be a more helpful use of the phone in diagnosis."
This is because the combination of sound and body position would help doctors determine if airways are obstructed due to apnoea.
Hearing
uHear
Free, suitable for iPhones
This app detects hearing loss by measuring how well you hear sounds at different frequencies, and how well you hear speech when there is background noise.
First, the app plays different sounds at different pitches, and you tap the screen when you hear them. A graph displays the results for each ear.
Part two of the test involves listening to speech against a noisy background. The app asks you to adjust the volume both up or down, until you can hear what's being said clearly.
Finally, a brief questionnaire gathers more details on how hearing is affected on a daily basis. Results are then plotted on a graph that compares them with what is 'normal'.
Expert verdict: This app could be a useful screening tool for people who want to assess whether they may have hearing loss, according to Tony Wright, emeritus professor at University College London's Ear Institute.
"But it cannot give a diagnosis of what may be causing the problem, so it's always best to see an ear, nose and throat specialist if someone suspects a problem," he says.
Heart rate
Know Your Heart Rhythm
Free, works best on the iPhone 5
One of the many apps that monitors your pulse, the Know Your Heart Rhythm app has been developed with the backing of the charity Arrhythmia Alliance.
It works by measuring how light is reflected by blood vessels beneath the surface of the skin. Blood vessels in our bodies rhythmically dilate and contract with every heart beat.
As tiny blood vessels, called capillaries, expand and contract in the tip of the finger, they produce colour changes that are not easily visible to the naked eye - but, under a strong light from a mobile phone camera, they can be measured by the app and used to calculate heart rate.
Fast, slow or irregular heart rates can suggest there is a problem that may need treatment.
Expert verdict: The Arrhythmia Alliance says the app is not designed to detect heart abnormalities but to encourage patients to seek medical help if their readings vary widely.
"We would never claim it is a detection device, but knowing your pulse is one of the best ways to pick up heart rhythm disorders," says a spokesman.
- Daily Mail
