Recently, a Reddit user created an application that allowed you to play Stadia on iOS utilizing the browser streaming technology that Google Stadia offered to its Stadia users. This application, called "Stadium," allowed for you to access Stadia, as well as providing BlueTooth controller support for those that wanted to use their wireless controller.
However, this feature was ultimately the downfall of the application. In an announcement from Zachary Knox, the one who developed the app, Apple has decided to remove the app from the Apple App Store, as it violates the App Store Policy. Apple objects to how the app extends "WebKit with native APIs to connect with Bluetooth." Apple later confirmed to The Verge that the application used Public API in a way it did not allow.
In a statement on Reddit, Knox mentioned that he is not upset at Apple. He also states that he will be releasing the source code to the public soon, making it open source.
Apple has been extremely objective to the ways that Cloud Gaming applications provide games to its users. Apple ultimately decided to block all Cloud Gaming applications unless they offer a different app for each game offered, which is just ridiculous. Cloud Gaming platforms like Shadow can stay on the iOS store because they pass themselves as a remote desktop application. Amazon Luna will be on the iOS store as a browser-based application that allows connection to the Luna streaming service.
Microsoft has already stated that they are working on browser streaming for xCloud, and they hope it will allow for their service to work on both PC and iOS. Google has not mentioned anything about officially supporting iOS in the near future.