With the US healthcare market valued at around $3-trillion, it's a relatively unexploited market for mobile technology. Apple rivals, Google and Samsung have competing health apps of their own, but neither has made significant headway with the establishments polled -- though Reuters does say that hospitals are interested in Google's Fit service, thanks to the high number of Android devices in use. Current trials are mostly using the data to monitor diabetes and hypertension, but with a certain watch just around the corner, the usefulness of HealthKit is likely to expand even more.