Tubecast is a full featured YouTube app for Windows Phone, which lets you watch, download and even play videos under the lock screen, and also lets you log into your account and comment, subscribe and all the usual YouTube cruft.
Unlike other apps, it also lets you cast video and audio to your TV, either via Chromecast or DLNA. This includes controlling the position of the video and the volume.
The app is free, but appears to offer only a limited number of “casts” (around 20) before you have to pony up $1.99.
If you are reluctant to pay, Tube Cast (with a space) is a free solution that has been stuck at Version 1.0 for nearly 6 months, but which will do an adequate job of getting your YouTube videos on the big screen.
Find Tubecast in the Windows Phone Store here.