Choosing a way to mesure heart rate ?

Hello i would like to make a led blinking that depend on my heart rate and integrate it on a clothe with a lilypad
But i don't know which material to use :
nRF24AP1 and Nordic USB ANT Stick with a heart strap (do you have one to recommend ?)
Or RMCM01 or Polar Heart Rate Monitor Interface (with wich heart strap ?).

And if you have any tutorial on this subject.

Regards and thanks
Bussiere