I use this app to check my resting heart rate every morning when I wake up, in conjunction with the Sleep Time app. This was easy with my old iPhone 5S. Now that I upgraded to the iPhone 7 Plus with the dual camera and the flash separated from the camera by a small distance, its almost impossible to measure! Azumio needs to update the app so that it only uses the lens closest to the flash so that both lenses dont need to be covered in order to measure. I wouldnt purchase this app if you have an iPhone 7 Plus until they do that.