Not sure if this helps but I found out yesterday you can use the Fitbit app with an iPhone or Apple Watch. You can also take part in the challenges. I know quite a few people who have Fitbits so I'll probably just dabble in that for the social aspects.
Again, not really relevant to the topic but thought I'd mention it.
Did you manage to get this working? I've been able to add both my wife and daughter without any issues... If you'd like to add me to check and see if it works let me know. The only (minor) issue I have is that there is a fairly long lag before the data updates.