"Play on" UPNP/DLNA device from OSX
Yes, you need to find UPnP Controller for Mac.
For example http://oss.linn.co.uk/trac/wiki/Kinsky is one of freeware. You can drag files to your UPnP device to play. Create playlist. Start streaming from UPnP server serources etc.
Hope this helps!
The closest I have found is www.skifta.com - you can use your Android phone to start videos from your Mac/PC to be displayed in your UPnP device. Which is almost OK for my needs. You just need to install thing in your Mac and Application in your phone. So phone acts like remote control between your computer and Media center.