I have only used Fitbit Charges for a study (fitness watch). It worked well. We registered the devices with Fitbit prior to giving them to participants so we were able to download the data. It tracked number of steps you take, your distance traveled, calories burned, weight, heart rate, sleep stages and length of time in each state, and active minutes. Newer devices also track location.

We have used plethysmography data. A plethysmograph measures blood volume in the subject’s thumb. We have used this data to detect emotions of the participants. But plethysmography measurement can also be used to compute the heart rate (HR). We have also seen that blood pressure and heart rate variability correlate with emotions. Further details can be found via Article Emotion Based Music Recommendation System Using Wearable Phy...