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A new feature! Why we made it and how it works.

A new feature! Why we made it and how it works.

We’re announcing a new feature….but first, let’s have some backstory and some science!

The back story:

Many mobile phone generations ago, back in 2016, whilst the middle of developing version 1.0 of Virtuali-tee for our Kickstarter backers,  I remember discovering that my phone (Samsung S6) had a pulse sensor built into it. Right next to the camera was a tiny little rectangular sensor, it had always been there, but I had never noticed it. It worked almost like magic, by simply placing my fingertip over the sensor the phone took my pulse rate and presented it to me.


Built in Pulse Sensor


At the time I thought it would be wonderful if all phones could do this, because then our Virtuali-tee app could track the wearer’s pulse rate, allowing them to visualise their heart beating live on their chest! I imagined all the wonderful experiments people could do with a built-in heart rate tracker, I thought about how this would transform how we learn about the important role the heart plays in our body into something really fun. It felt like a dream so close to coming true, but I knew the odds of every phone having an expensive pulse sensor embedded were slim...



Well, I was right about those odds, hardly any phones have a dedicated pulse sensor...but amazingly, I was wrong about the need for a special sensor! It turns out this same phenomenal technical wizardry could be achieved through a different sensor, one that all phones now have…….the humble camera.


The science:

As Arthur C Clark put it Any sufficiently advanced technology is indistinguishable from magic”...and he’s right, because this is far from wizardry. The science behind this is established and solid. The technique is known as “Contact Photoplethysmography” (pronounce Photo-ple-fis-mogra-fi). If you have ever been into hospital for an operation, and the nurse popped a wired clip over the end of your finger or toe, that will be a little, infrared sensor carrying out contact photoplethysmography.


A finger clip using Photoplethysmography


The method works by measuring the amount of light that is absorbed by your flesh, blood and bones. More blood absorbs more light, so as your heart beats and higher pressure/density blood rushes into your finger more light is absorbed.  The sensor detects this increased absorption and graphs it onto the ECG machine (the beep beep beep machine you hope doesn’t flatline into to beeeeeeeeeeeeeeeeeep.)

The new feature announcement!

So by using the same principles, it seemed that indeed we could bring pulse rate tracking into the Virtuali-tee app…..and we have! As of the 23rd of July, the app will update with a brand new feature: A heart rate tracker:



As ever, we’re doing things slightly differently. In the Virtuali-tee’s heart rate tracking feature we measure your pulse in almost exactly the same way, with the exception that we are using just the visual spectrum of light as supposed to infrared. The device camera produces a video feed, which once a fingertip is placed over the lens becomes bright red (either by surrounding light passing through the finger or via the devices flashlight LED). We then sample the image for regular drops in the RGB values of a sample set of pixels. Once we have a regular pattern we are confident isn’t the result of grain/noise, we map this to a set of animations and trigger the measurement cycle.

There is such a thing as non-contact photoplethysmography, which is via the analysis of the video feed and detecting colour changes in someone’s face. Quite remarkable stuff!

We can’t wait to launch this new feature of the app and look forward to the discoveries you’ll make into what affects your heart rate.


You can grab your Virtuali-tee on:

And don't forget to download the Virtuali-Tee App on:


Author: Ben Kidd - Co-founder of Curiscope, creator of the Virtuali-Tee


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