Apple has unveiled its latest mobile operating system, iOS 8, at its annual Worldwide Developer Conference (WWDC) in San Francisco.

The biggest addition is that of HealthKit, a centralised location for collecting fitness and medical data that is capable of integrating information from third-party apps and devices like the Jawbone Up fitness band.

The new HealthKit app is unveiled at WWDC.

Widely rumoured to be named Healthbook, HealthKit has already been integrated with Nike's running apps and the Mayo Clinic app, which will allow blood pressure to be recorded.

"We believe that Apple's HealthKit will revolutionise how the health industry interacts with people," said Dr John H. Noseworthy, CEO of Mayo Clinic. "We are proud to be at the forefront of this innovative technology with the Mayo Clinic app."

Apple will also work with other health organisations to allow users' data to be sent to healthcare providers in order to simplify and improve checkups. According to Apple, strong privacy protections have been put in place to prevent sensitive data from being lost or stolen.

iOS 8 follows on from the radical redesign of its mobile OS last year with iOS 7.

"iOS 8 offers simpler, faster and more intuitive ways to use your device with incredible new features like iCloud Photo Library, a new Messages app, the QuickType keyboard and an entirely new Health app," said Craig Federighi, Apple's senior vice president of software engineering.

"We're also giving developers amazing new tools to make managing your health and your home from your devices an integrated, simple and secure experience."

The QuickType keyboard allows users to access special layouts, character sets and supports predictive typing that learns from your activity to personalise autocompletion.

iOS 8 also allows for third-party keyboards to be installed, such as Swype. Third-party app integration has also been introduced for Apple's Tough ID feature, allowing users to sign into finance apps like Mint by swiping their fingerprint across the Home button.

As expected, Apple jumped aboard the home automation bandwagon that Google has until now been pioneering. The HomeKit feature lets iDevices communicate with smart thermostats, lights and doors. Partners already onboard include Phillips, Kwikset and Honeywell.

The new messaging app for iOS 8 includes an integrated 'do not disturb' feature for use in group chats, as well as a one touch audio and video recording button and a new ability to share user's location data.

Virtual assistant Siri also received a makeover, allowing hands-free recognition through a "Hey Siri" command, much like with Google Now. Siri also received Shazam integration, as was expected.

iOS 8 will be available immediately for iOS developers and as a free update for consumers this autumn.