Touchless heart rate monitor apps detect changes in face's reflectivity
By Darren Quick
September 5, 2012
There’s no shortage of heart rate monitor apps available for the iPhone, most of which take their readings by detecting the pulsating blood flow through a finger placed over the iPhone camera’s lens. But we’ve recently seen the release of a new kind of heart rate app that doesn’t require any physical contact with the phone as it takes its readings by simply looking at your face.
Heart rate apps such as Pulse Phone and Heart Rate by Blessed Apps (Free) work by monitoring the changes in the skin color and transparency caused by the flow of blood in a finger covering the iPhone camera lens. While still using the iPhone’s camera, more recent additions to the heart rate monitoring app scene, such as Cardiio and What’s My Heart Rate, measure one’s heart rate by detecting the micro color changes in your face caused by your heartbeat.
Cardiio’s creators claim their app is based on “cutting-edge research and science conducted at the MIT Media Lab” that showed that the increase in blood volume as the blood vessels in the face expand with every heart beat causes more light to be absorbed, resulting in a decrease in the amount of light reflected from the face. The iPhone’s camera can pick up these changes, thereby allowing the app to calculate a person’s heart rate.
Users need to hold the iPhone roughly six inches (15 cm) in front of them and line up their face inside a guiding box. The app also needs a well-lit area – and I mean a well lit area. I put both Cardiio and What’s My Heart Rate through their paces and, although I thought my room would be ok light-wise, both would only provide a reading when standing directly under the brighter lights in the bathroom. However, Cardiio did seem a bit more forgiving in this regard.
The instructions also warn that long hair covering the forehead will make it hard for the app to get a reading – unfortunately, this wasn’t a concern for yours truly.
Cardiio claims an accuracy of within 3 beats per minute (bpm) of a clinical pulse oximeter. Although I didn’t have one of these laying about to test this claim, my mother, a nurse for over forty years, was on hand to provide a reading the old fashioned way and Cardiio’s claims were confirmed. My mother recorded a heart rate of 75 bpm, while Cardiio recorded 77 bpm and What’s My Heart Rate 73 bpm.
As you can see, both the apps I tried were pretty accurate (if we take my mum as the gold standard, which I do) but an important point of difference is the price. Cardiio costs a premium US$5 in the iTunes store, while What’s My Heart Rate is free and is available for both iOS and Android devices. However, Cardiio does provide a few features that its competitor doesn’t, such as a potential life expectancy calculator (I apparently only have another 37 years) and the ability to track your fitness over time.
However, an in app upgrade to the premium version of What’s My Heart Rate costing $0.99 will add this feature, along with iCloud syncing capabilities and a breath rate monitor that works by tracking the rise and fall of your chest. What’s My Heart Rate also lets users switch between the front-facing or rear-facing camera, while Cardiio works exclusively with the front-facing camera.
It should be pointed out that both app makers point out that their apps are intended for “informational and entertainment purposes only” and shouldn’t be used instead of professional medical equipment.