Microsoft officially announced today that it will launch Cortana, a personal assistant present on Windows Phone and Windows 10, for iOS and Android. The announcement was made in a post on the Windows blog and, in addition to Cortana, the company released more information than it is planning for the near future.
The company's plan is to promote the integration of the new Windows 10 with the market smartphones, not limited to Windows Phones only.
But don't be scared: Even though different applications are similar for each system, Microsoft confirms that you can ask the same questions and searches on the different systems you own. The Android version should come out next month (June) and for iPhone by the end of the year.

Although Cortana on iOS and Android is not as powerful as Windows, due to various system integration issues, Microsoft has promised that it will also have notification support. You can set them up to receive information about sports, flights and most of the features Cortana currently supports for Windows Phone and Windows 10.
All of this will be centralized to a main Windows app called Phone Companion App, which will offer Windows features and services to all smartphones. The Companion App helps you install useful applications to use OneNote, store and access your files in OneDrive, save and edit Word, Excel, and PowerPoint documents with Office mobile, as shown in the video below.

[youtube https://www.youtube.com/watch?v=lXREpLewgOY&w=560&h=315]

How to test Phone Companion before everyone else? Sign up for Windows Insider Program and install a test copy of Windows 10, Microsoft stated that Companion will be available in the coming weeks.
Source: Windows Blog