"Microsoft has introduced Cortana for Android and iOS in the UK, a year after the digital AI platform was launched in the United States.
Cortana will compete with Google Now and Siri in Android and iOS devices and comes with several new features.
Microsoft claims its 'Edge' over Chrome and Safari
With this year's Windows 10 Anniversary update, Cortana can now be accessed even when the screen is locked and can perform functions like answering questions, playing music and setting reminders. Cortana can also remember things for you which you recently did and will let you add photos to make your reminders visual. The best part about it is that thanks to Microsoft's Continuum concept, Cortana works across devices, including Xbox, and can be synced accordingly.
The fact that Cortana works with the Bing search engine by default in Windows 10 devices begs a question if it will have to work with Google and Safari search engines in Android and iOS devices.
While the Cortana app for Android devices is now available to download, you will be able to download it on iOS devices in a month from now. Like in Windows devices, you will be able to activate it hands-free and a 'Hey Cortana' call should wake it up on your device."
I've used most assistants on mobile phones and for certain circumstances such as setting a reminder , an alarm or dictating a text I do find them useful.
My issue is I sometimes forget it's there to use !
Also when I'm out and about one can receive funny looks from other people when using these. Lol.
I think other factors to consider are the possible impact on battery life and the phones resources.