I have Looked at the mediaportal forum. There has been some projects about 2-way plug-in for pocket pc:s. See for example this thread:

[Link: forum.team-mediaportal.com]

But these projects were never completed. I think Megacrypto, a member on this forum , has used one plug-in for sending commands one-way from the Pronto to MediaPortal, don't now if it possible to use the serverside for 2-way. The server code for MediaPortal is in the thread in someone is interested.