UPnP/Client

XBMC's UPnP client (aka UPnP renderer) allows XBMC to instantly playback and control videos and music sent to it from a UPnP server and control point. This is similar to the AirPlay protocol, but more flexible and open. Several applications exist for nearly all major OSes that can send XBMC media through UPnP. This is different from using UPnP as a media source, where XBMC browses a UPnP server, rather than being controlled by one.

UPnP client settings
To turn on XBMC's UPnP client, in XBMC go to Settings -> Services -> UPnP and enable "Allow control of XBMC via UPnP".

Sending video to other UPnP targets
As of XBMC v13 "Gotham", XBMC can also be a control point in addition to being a UPnP server, allowing one XBMC device to control another.

It seems to only reliably work with other instances of XBMC at the moment, but the goal is to have it work on TVs and other UPnP and DLNA targets.

Download a nightly or monthly build, go into Settings -> Services -> UPnP -> Enable the "look for other UPnP" option.

Then when you want to play something, bring up the context menu while that video is selected, and choose "play with". That should give you a list, starting with DVDPlayer (local), and any UPnP renderers that XBMC is able to detect.

If playing to another instance of XBMC, remember to turn on the UPnP setting for allowing UPnP control (Settings -> Services -> UPnP ).

It's a little clunky at the moment, and it seems to not work with the most recent Monthly snapshot. I would recommend using an Alpha 4 monthly build until that is resolved. However, it does work, and it's pretty slick. XBMC still needs some tweaking in the UI to make controlling a little nicer, but that can also depend on various skinning options. For example, on Confluence you have to use the sidebar menu's "mini player" controls, but on a tablet using Touched or Retouched, you can use the full screen controls or the larger "mini player" controls at the top.