iOS: There are plenty of ways to check your heart rate, from expensive gadgets to just using your finger and a stopwatch, but none are quite as clever as Cardiio. You simply download the app, point it at your face, and it provides you with an accurate heart rate.
I had a hard time believing this was actually possible, and so I took my own pulse before using the app. The results were the same. Cardiio successfully reads your heart rate by watching the light reflected on your face. Once it has an accurate measurement, it will show it to you, and you can save it for future reference. It'll let you know how healthy your heart rate is and compare it with others. That's pretty much all the app does, but it's a little mind-blowing that it can get an accurate read from your face. If you have any need to track your heart rate, it's a wonderful addition to your iDevice.