Apple, will monitor your heart rate via the built-in microphone

A new iPhone application, currently awaiting approval from Apple, will
monitor your heart rate via the built-in microphone (through either
the onboard mic on the iPhone or through the mic/headset combo). The
developer has released the above video demonstration.

In addition to monitoring your heart rate using the microphone, you
can also count your bpm (beats per minute) using the voice prompts.
The application then stores your heart rate for later reference.