Program reviewed: Instant Heart Rate
Your smartphone probably has many sensors, but there is one that has become ubiquitous, being present in most “dumb” phones too, that should be considered the king of sensors: a camera.
It’s one there’s sure to be a lot of unexplored or poorly explored possibilities for: machine vision is only in its infancy, With Google Goggles and Shopper being among the most advanced examples for it that are available for Android, and Barcode Scanner being the one established use.
But there is something that doesn’t really require complicated machine vision, and yet that I’m sure most of us would never have thought of, that your Android phone can achieve using its camera: measure your heart rate. The popular program Instant Heart Rate manages to do that with decent accuracy on my Milestone.
It works using the same principle as a pulse oximeter: the transparency of your fingertips varies depending on the blood volume in the skin, so it’s possible using a camera to measure the resulting slight changes in skin color.
Of course there needs to be light for any transparency to occur; professional oximeters have a light source, a LED placed opposite the sensor (a photodiode, not a camera), to provide strong and constant illumination. Fortunately, your phone probably also has a conveniently-placed LED – the camera flash!
Since the flash LED is placed on the same side as the sensor, though, you will have to be a bit careful with finger placement and pressure: in my experience, the program works best with the fingertip just barely covering the lens, while completely covering the LED, and with almost no pressure applied.
If you don’t have a flash, or your flash doesn’t work, you can still try using the program in a very well-lit environment (sunlight, or a lamp pointed directly to your finger). Note that, on my Milestone, the program isn’t able to light up the LED for some reason, so I have to invoke Quick Settings and do it manually; I imagine any other “LED torch” program will do.
How to tell whether the program is actually working? You will notice that the little heart icon tends to beat regardless of whether there’s a finger anywhere. It will not, however, beat very regularly, and the number printed (if any) will keep changing. If, instead, you place your finger gently on the lens, try not to move it, and wait some seconds to let it stabilize, if you’re lucky the heart icon will start to beat in a more regular fashion, and the number will change much less.
To make sure it isn’t just some clever trick, you could also try it with someone much younger or much older than you: young people tend to have a much faster rate. Of course you can also check against a real heart rate monitor. My experience is that Instant Heart Rate isn’t necessarily very accurate compared to a real instrument, but if I compare the numbers between myself and other people, it’s clearly not making stuff up.
Thus, this application might not be immensely useful, but your mileage may vary depending on details of your camera and flash, and it’s good enough for a quick check of whether your heart is drumming way too fast.