I've finally placed the Polar chest strap receiver chip and Open Heart LED matrix on the Adafruit data logger shield:
Quick video while I'm sitting at rest:
The Adafruit shield has a SD card accessible via SPI and a DS1307 RTC via I2C. I'm working on the code write now to log the heart rate data to the SD card and hope to have it done in a day or two. I'll post it here then. After that I'll try using gnuplot on a computer to make graphs of the data.
Here's a couple more shots of the shield. I used female headers for the Open Heart and Polar chip as I wanted to be able to remove easily if needed. The crystal for the Polar chip is actually soldered underneath the shield as I was at first thinking I would lay the Polar chip flat on the prototyping area: