I recently purchased a Charge 2, with the primary purpose of recording my sleep patterns.
In the first instance, I am quiet disappointed with the sleep tracking functionality:
1) Sleep stages does not work; and
2) The sleep data is inaccurate.
I generally find myself being in and out of bed quite frequently, on account of insomnia issues. Last night during a period of around 1.5hrs, I recorded approximately 300 steps and 2 flights of stairs, which is accurate, as I was awake. The corresponding time period for the sleep tracker indicated that I was either asleep or restless. It does not appear that there is any integration between the activity and sleep recording functionality. i.e. Generally, I'm most likely not sleeping, whilst recording steps, and definitely not sleeping if I'm walking up and down stairs.
Additionally, Laying or sitting still, whilst awake, is being recorded as being asleep.
