Health: it's stepping on the toes of many partners, but might be groundbreaking. It's extremely hard to crack healtcare, it's very closed, defensive system of people and bureaucracy, Apple might just have the power to do it.
Extensibility: intents are basically _the_ reason Android can work so much better in many cases than iOS. I hope MS will bring it to WP very soon.
Per Healthcare: that is a really exciting new feature and there is a LOT of potential here. But I wonder how successful it can actually be in the grand scheme of things. I.e. not everyone can have or wants an iPhone.
Edit, expanding a bit:
On the flip side, I am huge advocate for personal health records (http://en.wikipedia.org/wiki/Personal_health_record), but no one really knows about them and no really uses them because they don't work with your doctor. I don't think Apple has even remotely come close to solving the overall problem of integration and usefulness, but maybe it will get more people interested and thinking about the concept of a personal health record.
Re. Health: it can fly in the US, and if it does, then they've got the momentum to port the stuff to other mobile OSes. Health itself is such a big industry that they might not want/need to use it just as a promoter for their devices.
Yes Apple will have an iWatch but they would be more than happy having hundreds of dirt cheap equivalents that integrate seamlessly with the iPhone.
A cheap Android device could be used to help monitor the health of an elderly relative, however do you really perceive people leaving the latest iPhone with their dementia stricken parent?
Are expectant mothers going to be happy with having wireless transmissions constantly next to their unborn child (regardless of safety records)?
Are nurses going to have sterilised iPads for for the ward, where fluids are abound?
Health monitors haven't taken off because people do not care enough to want constant monitoring.
Edit: spelling
When (not if) this happens with HealthKit/Health, it'll be slightly disappointing to see these kinds of integrations from behind a glass window. At least some aspects of HealthKit are already being integrated with major fitness companies (namely, Nike), so not everyone will miss the boat entirely.
Hopefully HealthKit will integrate well enough with third party hardware that you can do a lot of the stuff yourself and then bring the data to your doctor when you need to.
tort reform freudian slip?
Care delivery is also an industry in which Apple has virtually zero market share - it's Microsoft through and through. Inpatient and outpatient EHRs all target Windows, hospital IT all runs Windows Server, and some of the more "forward-thinking" hospitals are even eyeing Windows tablets (I kid you not).
Potentially huge upside for them (which is obviously why they want to do it), but it's very difficult to penetrate, and they have almost no foothold there so far.
I believe this is primarily because the development environment is really simple for this class of software. Platforms such as .NET, COM, MFC and VB have been around a long time and it's easy to find programmers. It also doesn't hurt that the desktops running Windows are incredibly inexpensive and easy to procure and run Microsoft Windows.
But targeting the end users of healthcare (e.g. patients)... that's something else entirely which only recently has started to have any traction.
That said, what Apple announced was patient data collection support in the client OS. App developers take care of shipping it to physicians and hospitals. Apple isn't taking the patient's information the last mile to physicians themselves.
Disclosure: I'm a co-founder of a startup dedicated to improving mobile patient and physician communication (Care Thread, http://www.carethread.com). We already integrate with hospital and doctor's office workflows, and we've been looking forward to the introduction of this feature in order to collect relevant patient data.