Your smartphone has a secret superpower: With its camera and flash alone, it can measure your heart rate. That means that apps are available to track your heart rate, with the aim of helping you improve your health.
This simple process has a complicated name: photoplethysmography. Every time the heart sends a pulse of blood through the body, the tiny capillary vessels in the skin expand. When a smartphone's flash illuminates the skin, its camera can capture the miniscule color changes that happen each time the heart beats. (Because you have to hold fairly still for this process, these apps don't provide the sort of continuous monitoring that external heart rate monitors can provide; with these apps, you'll have to stop what you're doing for about 10 seconds to take your pulse.)Dozens of heart rate monitoring apps take advantage of smartphones' built-in ability to provide a quick and easy way for users to take their own pulse — no math required. We recommend looking for one of these apps. Some heart rate monitor apps on the market require users to take their own pulse, tapping their fingers on the screen with each heartbeat. A few are simply timers that do little more than tell you how long to count your own heartbeats. There is little point to downloading these apps, as they don't save much trouble over simply taking your own pulse.