There is a new Universal Xbox Live app for Windows 10, which has already been seen on the desktop, but so far has not been available on Windows 10 Mobile.
WindowsCenter.ir however managed to get their hands on the software running on a handset, and have posted images and video of the app in action.
The app brings support for chatting with Xbox Live friends, watching Twitch broadcasts, Game DVR (I suspect watching, not recording), changing your profile pic, finding friends and more.
The leak likely indicates that the next version of the Windows 10 Mobile Technical Preview will include the software on release.
See a brief video showing it in action below.