Despite all that, the official response is negative:
We do not currently have plans to integrate with HealthKit.
It is an interesting new platform and we will watch as it matures, looking for opportunities to improve the Fitbit experience. At the moment, we’re working on other exciting projects that we think will be valuable to users. The question we want you to keep in mind when providing feedback is: What do you imagine a HealthKit integration would entail and what do you expect to get out of it?
Your voices are being heard. We’re actively reviewing your responses and providing feedback to our product development team.
Join the discussion here: http://bit.ly/1ndlXdI
Update (9/10): Fitbit is starting to think about this further, with the feature request now marked as “under consideration”, and the following note added
At Fitbit, our mission is to help people lead healthier, more active lives, so we’re always looking for ways that our users can use their data to support their fitness goals. For the past few years, we’ve been the leader in developing direct partnerships through our open API with hundreds of the most popular health apps, wellness programs, incentive systems, and other services that have enabled our users to make the most of their Fitbit products and data. Because of this commitment to connect with other applications, HealthKit is really interesting to us. Since its announcement, we’ve been evaluating integration with HealthKit as more of its features and benefits are revealed.
Fitbit remains committed to supporting all of our users, whether they sync their Fitbit products with iOS, Android or Windows Phone devices, Macs or PCs. While HealthKit works only on the iOS platform, we also plan to maintain direct integrations with our partners so that Android, Windows Phone and PC and Mac users in addition to our iOS users can benefit from our partnerships.
Please share your thoughts with us. We want to understand how you envision an ideal HealthKit integration to work and what benefits you’re hoping for. We’re actively reviewing your responses and providing feedback to our product development team.
It is true that Fitbit is connected to many apps and platforms to exchange data. But this is mostly done after specific agreements with the companies behind these apps. There is also an open API and even a IFTTT channel that will give tech enthusiasts their data. But the HealthKit integration would mean giving up some control over which company gets to benefit for Fitbit users…