We’ve just connected the Polar strap heartrate monitor we borrowed (along with this interface: https://www.sparkfun.com/products/8661? ). This website has very clear instructions to get started with the interface: http://bildr.org/2011/08/heartrate-arduino/
Here is my heart-rate (beats per minute) over the course of 10 minutes, while winding down before sleep. I noticed the highest peaks happening when I took deep breaths or yawned.
It will be interesting to monitor the heart-rate over the course of the next few days during more stressful situations. The next step is to figure out how to communicate this information dynamically with a website…