The problem with rdesktop or VNC is that you are actually taking over the remote computer. If the resolution is greater than 800 x 480 on that machine you have a lot of scrolling to do to interact with the desktop.

HumanPenguin's got it right with forwarding X to the tablet. I have been using this method to control Rhythmbox on my home PC which outputs its audio to my wireless home speaker system. By forwarding X from the desktop to the tablet, I am free to create playlists, next track, rate, submit tracks to last.fm, fetch lyrics, etc all from tablet, anywhere inside or outside of the home. And since X is so well thought out, resolution is not an issue. The application is automatically resized to the size of the tablet's display. To me, this is a much more elegant solution than rdesktop or VNC.