I just bought the Fitbit Charge HR and its OK, but I wish I spent a little more and got something waterproof and compatible with Google Fit.
First the waterproof part. I originally wanted something with a heart rate monitor that I could wear kayaking, because the fitness apps can't figure out calories burned kayaking. Then I started running and wanted something for running and forgot about waterproof. The fitbit was recommended by friends for running so I bought it. Then I read the specs after vs before and fuck, I can't wear it swimming so no kayaking, cause shit happens. Again, read the specs and reviews before you buy.
The Android app has a lot of features but it can't share data with google fit yet. You have to use the fitbit website to edit the name of a workout downloaded off the fitbit. When tracking your exercise it only tells you how long you worked out, but not the start and stop times. So you have to guess what time something happened when you manually add things, like swimming when all you know is I swam after the treadmill but before the bike rode home, and was this one the bike ride or that one?
Also if you go outside and cut your grass using your riding mower for an hour, when you come back in you may find that fitbit counted it as an hour of exercise, but Google Fit does the same thing. You can edit the name from the fitbit website, but you can not tag it as not-exercise, all you can do is delete it. If you could tag, fitbit and google could learn from it.