I have an xbox doing everything that your Philips SLM5500 is doing. Included with that setup is a web interface to the xbox media center
http://www.xboxmediacenter.com/wiki/..._Web_Interface
allowing remote control of the xbox from anything that can view the web page that it is serving.

However I dug a little deeper into the MP daemon. You can set it up to output a ShoutCast stream to your Philips SLM5500 which you could then control with MMPC for the n800 http://mpd.wikia.com/wiki/Configuration look under Icecast.