The Washington Post said that Clue, a popular app women use to track their periods, has risen to near the top of Apple's Health and Fitness category. Now Apple plans this month to incorporate some of Clue's core functionality such as fertility and period prediction into its own Health app that comes pre-installed in every iPhone and is free.

Clue earnt money selling subscriptions and services in its free app.

The threat to Clue shows how Apple plays a dual role in the app economy: provider of access to independent apps and giant competitor to them.

It has created a system where developers have come to accept that, without warning, Apple can make their work obsolete by announcing a new app or feature that uses or incorporates their ideas.

So how does Apple get away with this? Firstly, it has a lot of cash to spend on lawyers who have instructions to take the case to the Supreme Court and secondly they might face consequences because they are dependant on the platform.

The Post said that this imbalance of power between Apple and the apps on its platform could turn into a rare chink in the company's armor as regulators and lawmakers put the dominance of big technology companies under an antitrust microscope.

“When Apple made a flashlight part of its operating system in 2013, it rendered instantly redundant a myriad apps that offered that functionality. Everything from the iPhone's included "Measure" app to its built-in animated emoji were originally apps in the App Store,” the Post wrote.