Fitbit Alta Fitness Tracker, Silver/Plum, Small 

I have owned the Fitbit One, Fitbit Flex, Garmin Vivofit and now the Fitbit Alta. Out of all of these, the Alta is my favorite. The Fitbit application is much better that any other out there, this is why I came back to Fitbit, even though I was satisfied with the Vivofit. My favorite feature of the Vivofit is that you replace the battery once every year and a half and you never have to worry about charging. With the One and the Flex I had to charge it up every few days and it was frustrating because right when I needed it, it would go dead. To my pleasant surprise, the Alta is lasting over a week between charges. One thing I did, was to switch off the all day synchronize with my phone. I think that this is likely what's given it such longevity. I've changed the screen from the default and now I have nice big letters and numbers that are very easy to read. I've been using it for a little over a month now and am very happy with this purchase.