Question: what is the difference between vivofit 2 and 3?
Answer: Whereas the Vivofit 2 uses two cells to power the unit for a whole year, the Vivofit 3 needs just a single battery to achieve the same life span. It's not a huge difference but does mean you get to save some pennies or cents on batteries over the course of using a Vivofit as your wearable of choice.