ResearchKit is an open source software framework built with medical research in mind. Basically, it makes it possible for an iPhone to be used as a medical research device and enables researchers to easily create apps to help with their work. Data is securely collected by anyone willing to contribute, and it is possible to control how much of a contributor's personal data is accessed.
Some of the applications demonstrated at the event included diagnosis of Parkinson's disease – an iPhone's sensors were used to detect irregularities in a patient's speech and walking. The possibilities, however, will be way beyond the scope of these tests once ResearchKit is out. It is scheduled for release in April so keep an eye out if you're willing to contribute in obliterating some of the nastiest diseases in existence.