You probably shouldn't use it as a full-time replacement, but in-between regular checkups with your doctor you can use Philips' new Vital Signs Camera App with an iPad 2 to easily monitor your heart and breathing rates.
Unlike most heart rate monitoring devices that require you to wear a chest strap or something around your wrist, the Vital Signs app simply has you sit in front of your iPad 2, holding still, while keeping your face framed in an on-screen box. The app looks for subtle colour changes in your face called micro-blushes caused by the blood rushing in and out, and simply counts them to calculate your heart rate.
As for your breathing rate, measuring that's a little easier and probably more accurate. You still need to sit still in front of your iPad 2, but instead of looking at your face the app tracks the movement of your chest and shoulders to determine your breathing rate. Both measurements can of course be shared with your friends via Twitter or Facebook, or emailed off to your doctor. And I'm sure they'll love getting panicked messages in the middle of the night when a one dollar app tells you your heart rate may not be ideal. [iTunes via The Verge]