Just heart rate - I believe it's logged at 5-second intervals during rest, and 1-second intervals during physical activity. I'm trying to get Python Fitbit working to download my HR data but am having API issues: http://python-fitbit.readthedocs.org/
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.