Make Magazine has an article about how to set up a Pocket PC as an auxiliary display for a notebook PC. In a fairly tongue-in-cheek manner, they strap the PPC to the top of the laptop, a-la some of the Longhorn mockups.
Personally, I reckon Innobec SideWindow (the software that makes this possible) would be an awesome solution for a Media PC remote. SideWindow connects via Activesync, which in turn can use USB, Bluetooth, or WiFi to connect to a PC. Having a PPC connected via WiFi, with direct screen access to the Media PC sounds like the ultimate solution to me. Sexy too if you go with Make’s suggestion and use Konfabulator for the on-screen widgets.