Would like to learn more about Cortana Triggers

[Doctor_Who]

Tonight while reading through my emails, I got a notification about something called Cortana Triggers. I went through the little tutorial and it looks like an interesting idea. I did this on my Windows 10 desktop.

So then I went to my phone, currently Windows 10 Mobile. I went to the store and found Cortana Triggers there as well - for about $5.

Is it free for desktops/laptops but not for phones?