I replaced my vivofit 3 with the vivofit 4 and absolutely love it. Easy to read outside and the new wristband with buckle assures me that i won't lose it as I lost two previous ones with the old closure.

I had to buy an aftermarket band -- large band was not available. These are great activity trackers -- when they are working.
For the price they can't be beat, just not as durable as I feel they should be

It does very little. The screen is extremely small. You have to punch the button repeatedly to step through the various "Pages" it shows you. There is a terrible notification feature from your phone re calls or messages - simply a green line on the small display alerting you to check you phone for the actual activity. I am returning mine for something more robust.