Adding XBMC as a Metro "Play" target in Win8, step-by-step
So if you run XBMC as your main media device and own a Surface, you'll find these instructions very helpful.
Usually XBMC will not show up in the metro Devices charm as a Play target because only Microsoft certified devices get this privilege. Fear not, after you follow the instructions HERE it will now show up!
Hopefully you are tech savvy enough to follow what amounts to changing the permissions on a reg key and creating a registry entry for your XBMC device.
What this allows you to do is play media from any metro app to your XBMC session on your TV. The example below is MetroTube open on the Left with the XBMC Remote snapped to the Right. So I can play content from YouTube to my TV and control, the volume and play/pause with XBMC RT. +1 for multitasking!
One little hitch is that you actually have to start the media playing before you go to the devices charm; for any play targets to show up. It does restart the video after it sends to XBMC so you won't be missing the start of everything!
Also, and this might just be my setup, sometimes the XBMC target will get stuck in a "playing" mode after your YouTube video is finished. I haven't figured out how to free it up without restarting Metrotube. If you know how to do this please share!