The parralel debug package from teknema keeps getting mentioned here by transiit and others, so I though I'd share my experience with it.
The first step was to install a minimal (no X) RedHat 5.2 system on a free partion. Add it to your lilo set up and boot to it and you can build the package, and insmod the new lp module according to the instructions.
Now, get out the soldering iron and rip up some old parralel cables to make the debugger cable.
I hooked this up to both a webpal and a daewoo (green) internet TV and got no response with the dubugger from either.
This was several months ago that I tried this and I don't rember all the details, but I was left with the impression that the debugger was written for 2.x version teknema boxes and would not talk to 1.x boxes like the webpal or daewoo.
The package does include tools for converting an .erx image into one suitable for downloading via the parralel cable, and someone who is handy with binutils might be able to generate some clues to the .erx format from studying them. The tools seemed to work on the RH6.2 system just fine.