What is Rygel?

Rygel:

* is an implementation of the UPnP MediaServer V 2.0 specification[1]
* is designed for GNOME desktop.
* is based on GUPnP[2].
* supports plugable Media providers (and currently has a tracker[3]-based media
  provider).
* is written (mostly) in Vala language[4].

[1] http://www.upnp.org/specs/av/UPnP-av-MediaServer-v2-Device-20060531.pdf
[2] http://www.gupnp.org/
[3] http://www.tracker-project.org/
[4] http://www.vala-project.org/