Apple launched the WatchKit set of tools to allow developers to support its new Watch wearable device, alongside several health and fitness apps optimised for the hardware.

The WatchKit includes tools and APIs for developers to build apps that exploit the capabilities of the Apple Watch. Currently these include actionable notifications and ‘Glances’ that provide users with timely information.

Apple announced that the likes of Facebook, Twitter and Pinterest, BMW and American Airlines have partnered with the company to develop apps using the new technology.

More advanced capabilities will be available next year when developers will gain the ability to develop fully native apps for the Apple Watch.

Unique features of the Apple Watch that developers will be able to tap into include the “digital crown”, which enables users to scroll, zoom and navigate the interface on the devices. It also features an accelerometer, in-built heart rate sensor, and GPS.

The Watch apps introduced by Apple included Activity, which is aimed at motivating wearers to be more active throughout the day by measuring calories burned, brisk activity and how often wearers stand up.

And its Workout app provides metrics needed during exercise, such as pacing and goal setting.

Apple also revealed that it now has more than 1.3 million titles in the iOS App Store, up 100,000 since June and from the one million reported in January. The App Store receives more than 300 million weekly visitors in 155 countries.

Alongside the Watch and the two versions of the iPhone 6, Apple also announced that iOS 8 would be available from 17 September as a free software update.

Touted as the biggest release since the App Store when unveiled in June, the new operating system includes more than 4,000 new APIs — including HealthKit, HomeKit and TouchID — for developers to use.

It also supports extensibility features that enable apps to extend and communicate with each other while remaining contained in their own sandbox.

This could enable the sharing of content from the Safari browser to the Pinterest app, the use of photo filters on images contained outside an app, or for the Bing translation functionality to be applied to web pages within Safari, for example.

The App Store is also accepting submissions for products built using Apple’s next-generation programming language, Swift, which was unveiled at the company’s World Wide Developers Conference in June.