Amazon is bringing Alexa Announcements to Fire TV devices in the UK. Already available for Echo devices (as well as Fire TV in the US), Announcements enable you to use your Echo network as a one-way intercom. Think a railway station/supermarket tannoy for your house and you get the picture.
When enabled, you'll be able to press the microphone button on your Alexa Voice Remote and say “Alexa, announce...[what you want to say]”.
Amazon has also announced it will be bringing the YouTube app to the remaining Fire TV devices that don't already have it - it was previously restricted to Fire TV Sticks and Fire TV Cube. The YouTube app should appear in the Apps and Channels row on your Fire TV home screen.
Alexa Announcements are only really needed for larger properties we'd say - but they can be useful to say that dinner is ready, it's five minutes until you need to leave the house - that kind of thing. You can even type announcements into the Alexa app. If you're clever and use Amazon Household, you can even do announcements between devices registered to different people but in the same house.
To manage announcements, go to Devices in the Alexa app and toggle Announcements in the Communication settings for that device. It won't broadcast to devices where Do Not Disturb is enabled.