As plays for the wearable and fitness space go, iOS 8 HealthKit is ambitiously broad. Apple will initially support logging of over sixty different types of data, from the basics like weight and gender, through step-counts and blood-glucose levels. By leaving the collection to accessory manufacturers - at least initially, anyway - Apple can safely be comprehensive without having to fill each of those gaps itself with dedicated hardware, throwing itself into the center of the argument over privacy versus aggregation.
Instead, HealthKit is a central repository for your health logging, a single database into which apps and services can connect to feed in information and check it out.
Perhaps unsurprisingly, opting for Apple’s ecosystem comes at a cost: if you want to tap into HealthKit, then it has to be the place where the data your users collect is kept. Think of HealthKit as a hub and spoke system, rather than a mesh of apps and services talking the same language, with Apple at its heart.
That’s not necessarily a negative, of course. Accessory manufacturers could feasibly launch without having to build an app themselves, relying solely on HealthKit instead.
It also leaves Apple responsible for managing privacy, and with the sanctity of health information such a hot topic - and one already blamed for derailing electronic medical record projects in several countries around the world - that’s something the company isn’t taking lightly. There’s the strong encryption you’d hope for, but also a range of privacy and access controls developers must abide by.
Apps can be given read but not write access, and it’s all done on a per-data-type basis rather than blanket approval one way or the other. Your pedometer and its companion app might be able to read and write steps but not your pulse rate, maybe, or perhaps allowed to read blood pressure data but not write to it.
Even how those limits are communicated to the apps has been considered. Developers can see whether they have sharing or write-access to a particular type of data, but they don’t see which the user has denied access to. For instance, a diabetic user might not want all of the services they engage with to know that they’re regularly using a glucose monitor.
For the user, it’s a row of the familiar settings toggles that turn on and off permissions on their iPhone (HealthKit won’t have iPad support at launch). It’s too early to tell whether Apple’s balance of granular control and approachable simplicity for HealthKit privacy settings will strike the right chord with users.
What Apple hasn’t discussed so far is more wholesale extraction of data: whether HealthKit users will be able to migrate from the platform to something else, and take their historical data with them. Without that, it’s potentially a new level of platform lock-in, keeping users to iOS not just with apps, but with their own health history.
The wearable market already dissuades people from jumping ship, even between relatively fragmented niches like Jawbone’s UP, Fuelband’s Flex, and other products. If you change your fitness band today, for instance, the biometric and activity history you built up with Jawbone won’t be transferred over to your Fuelband account.
To some extent that’s worked in the device manufacturers’ favor so far, but HealthKit threatens to lift the lock-in up the chain. Any health device manufacturer will be able to not only tap into HealthKit, but to compete directly with their rivals by picking offering a new wearable that picks up exactly where the old one left off. No interruption in logging, no lapse in statistical analysis, and no route away from Apple as essentially the gatekeeper of the data.
More on Apple and the WWDC 2014 announcements in our Apple Hub