Still, it could be worse - couldn't it, Japan?
To recap for our Euro-pals, the iOS and Android companion lets you access the PlayStation Network to chat with friends, compare trophies, purchase stuff on the store, access system guides, and a fair bit more besides. It also syncs up with the PS4 in various ways, including as an on-screen keyboard,and by offering the same Second Screen functionality (note: not Remote Play) that the Vita provides with certain PS4 games.
Sony also detailed that 18 apps will be available on the PS4 across the European launch, although a lot of them are limited to certain countries. The UK will get BBC News, BBC Sport, BBC iPlayer, and Demand 5 apps, for example, and there are similar TV-based apps for specific countries like Germany, Belgium, and Spain. As for the more generally available apps, they include IGN, Netflix, Music Unlimited, Video Unlimited, and VidZone.
The PlayStation Blog has the full list of apps and the countries they'll be available in.