Exactly, somehow the light can measure your heart beat. I know this app.
The pulse in the blood flow causes variations in brightness, that's what it detects. The Casio HRM watches work in exactly the same way. So it should work with any smart-phone that has a camera and LED flash.
I prefer blood pressure measurement. Some of you can hope for a glucose checker.
Don't think you can do that optically. AFAIK it usually involves taking a blood sample and putting it on a slide or stick of some sort. Not sure how accurately you can measure blood pressure though, not without the usual inflated cuff. Any blood pressure monitors I've seen always have a cuff that inflates.
This has got me thinking if I were to buy a flagship Samsung, I might as well get the S4 rather than the S5. The S4 is very likely to be reduced in price when the S5 is released. Especially given the apparent reduced storage availability in the S5 compared to previous S series flagships. And that the heart rate monitor is a free app you can just install.
Keep in mind the S4 did not sell as expected and was a huge jump from the S3.
