If you don't know how or what HRV can be used to help performance and measure recovery these couple article will give you a quick cliff notes version of the basic concepts. Well written by Mike T. Nelson. I believe these were part of the PaleoFX meetings this year. Enjoy.
Using Heart Rate Variability Part 1
Using Heart Rate Variability Part 2
Here is an interview that Joel Jamieson did about HRV with swimming. Joel is the creator of Bioforce HRV a type of system that measures it. Joel Jamieson Discusses HRV.
Here is a round table on Tnation. This has some of the best minds in the business discussing HRV.
I've personally just purchased an Ithlete finger sensor to see about testing a few patients. This seems much easier then strapping a heart rate chest strap on. I will blog at a later date on my opinions/findings.