• 08.13.12

Heart-Monitor iPhone App Works By Scanning The Blood In Your Face

To describe a Cardiio, inventor Ming-Zher Poh invokes Arthur C. Clarke, who once said that “any sufficiently advanced technology is indistinguishable from magic.”

Heart-Monitor iPhone App Works By Scanning The Blood In Your Face

There are plenty of gadgets out there that can accurately monitor your heart rate during exercise–Amazon lists hundreds of watches, chest straps, and finger clips. But Cardiio, an iPhone app from a group of MIT and Harvard scientists, may trump all of them. Thanks to recently developed optics technology, Cardiio is the first heart rate monitor that needs no connection to your body to read how hard your heart is working. Instead, the app uses the iPhone’s camera to get a reading on how fast blood is pumping to your face, and remarkably, comes up with a nearly perfect BPM estimate.


Cardiio is the invention of Ming-Zher Poh, who was a PhD student at MIT’s Media Lab when he first began studying how computer vision and advanced signal processing could detect a subject’s vital stats. How? Well, every time your heart beats, the blood volume in your face increases. Though it’s not visible to human eyes, digital cameras can detect the change, since a face with a higher blood volume will absorb more light, and conversely, reflect less light back at the camera. Poh designed an algorithm that captures video of your face using tracking software, then distills it into RGB channels that are analyzed to determine a rough BPM based on reflectivity. Studies show that the technology is accurate to within three beats per minute.

“The idea came about back in 2009,” Poh tells Co.Design. “My research focused on unobtrusive physiological sensing and I was building wearable devices to measure heart rate using light.” His prototypes included a pair of brilliantly-named “Heartphones,” as well as magnetic earring sensors. A later design, called Medical Mirror, embedded his facial tracking software behind mirrored glass. Anyone standing in front of the frame sees an LED display of their vitals. The idea is to make monitoring your own health an easy, and even fun, part of every day life. “As ordinary people start to have access and control over their own physiological data, they can play a more active role in the management of their health,” Poh and his team write in a 2009 study on the mirror. “This revolution must take place in our everyday lives, not just in the doctor’s office or research lab.”

Cardiio is the first commercially available version of his algorithm. Hold it up to your face for a few seconds, while you’re exercising or simply curious, and the pulsing HAL 5000-esque orb gives you a quick BPM read. Then, a slick user interface visualizes your stats in context with your history, and lets you compare yourself to other users. It even (somewhat ominously) calculates your life expectancy in relation to your fitness level.

Though it’s only a few days old, Cardiio is already one of the top-rated health and fitness apps on iTunes. “The reception has been amazing,” says Poh. “As we’re working on further advancements of the technology, it could have a great impact on telemedicine and home health monitoring. The idea is to make a health check up as simple and unobtrusive as possible. That makes the process of tracking your health less of a dread, and perhaps even delightful.”

[Image: Malota/Shutterstock]

About the author

Kelsey Campbell-Dollaghan is Co.Design's deputy editor.