Heart Rate Sensor.

it some how began posting from an accidental key press....

Basically, using an IR Sender/Receiver I feed the output to an opamp and feed it into Arduino.

Using the heart rate, could be a very useful tool.... how's this for a thought, use that data have it delivered
to a PC, and have the heart rate dictate the music that is played?.....

EG Fast beat = you need to be calmed down
Slow beat = Fast track, to perk you up (unless you're dying then i suggest you call an ambulance not play music)