Do activity trackers work?

# Further details on topic is attached.
# No introduction. No conclusion.
Requirements are as follows:
1. Draw a box-and-arrow diagram of the theoretical concepts in you research (e.g. what health benefits can be expected from activity trackers?). How do you plan to operationalize these concepts into independent (cause) and dependent (effect) variables? Comment on the reliability and validity of your measures. (one page)
2. Besides activity trackers, what other factors might affect the health benefits identified above? How would you control for the effect of these factors, so you can safely attribute the observed benefits to the use of trackers? (two pages)