I've got https://github.com/magnific0/FitBit.py working (with a minor tweak - the refresh token path is missing a "return", it seems) for downloading my heart rate data. Works great.

https://rjp.is/experiments/heartrate/buckets5.html https://rjp.is/experiments/heartrate/minsum.html

Drop me a note (contacts in profile) if you want a copy before I get around to github'ing the changes.