Riot Studios has the worlds most popular and most played game League of Legends to manage, so its too surprising that it took them until 2016 to get a mobile app out. The new app called League Friends does a myriad of usefull things. You can use it to chat with your friends who are playing league, you can have it push you notifications for when you are invited to play a game of league, and well thats it. But, its a young app, so give it some time to grow
Riot promises that they will expand the functionality of the app sometime “soon” to include stats and other useful features. The app is now available in North America and Oceania, with other regions to follow shortly after. You’ll need either iOS 8.3 or Android 4.1.1 (or newer iterations of these) to run it.