Looking to buy a Fitbit and need some suggestions

The fitbit devices are made accessible through the iOS app. The app is generally quite usable, and all the various metrics can be read.
As for the hardware, You can skip the Blaze and Surge as they have inaccessible watch-like features. Otherwise, pick the one that has the features you want. Want heart rate tracking, choose the Charge 2. Want waterproofing, the Flex2. For fashion, choose the Alta. None of the devices are accessible natively, though they all have vibration for alarms, goal reaching, switching between modes, etc. Also note that the devices with screens will require sighted assistance to pair initially, as you have to enter a pairing code from the display.

Although I actually went with the Apple Watch because it was a gift, before I received the watch, I had already decided to go with the Charge 2 because of the heart rate data. Also, during my research, I discovered that you start/stop your exercise time by the press of a button, which is the only thing you can do with the device itself. Otherwise, as the above post states, all of the exercise stats are available through the iOS app. I think that the Charge 2 is the best selection specifically for a blind individual. I would have preferred the Surge because it really appealed to the nerd in me, but the features that it boasts are sadly not accessible, thus not worth the additional expense.

Now then, if you would want much more accessibility on so many levels, including your exercise data, I highly recommend the Apple Watch. I am so delighted that I received this gift. I am quite impressed with all the different metrics I can see throughout my day, with regard to my exercise progress. Of course, it's so nice to be able to set timers, alarms, catch the weather, check my calendar and so much more on the same watch. There certainly isn't anything wrong with the Charge 2, but if you want much more out of one device, add a few dollars and get a much better investment with true accessibility built in. With the Charge 2 you are completely reliant on the Phone for everything, but the Apple Watch has VoiceOver baked right in. If your wallet will allow it, I suggest the Apple Watch series 2 because you will not have so much VoiceOver lag time and it's also waterproof and has a much faster processer than my series 1 does.

HTH