Cardiio
Is it magic? We're not sure, but we are sure that Cardiio ($5) can do something it shouldn't just by looking at your face. Based on MIT technology, it measures when your face is reflecting more light and when it's not, giving you a semi-accurate idea of your heart rate without ever having to strap a single sensor to your wrist, chest, or nether regions. [Scouted by Richard]