The JoyTech 9200 Digital LCD Monitor for the Xbox 360 (full specs here) looks like it has pass-through possibilities for modders (watch somebody build it right into the case), but it's too bulky to be sleek, and too small to replace that 80'' plasma in your living room. Still, slapping it over the vent holes on your console might be a good way to test your over-heating issues. How do they get away with advertising this thing as "high-definition" when it has a 800x480 display? I guess with a 9'' screen, it doesn't really matter.
Of course, if you only have $180, anything would be an improvement over the miserable displays in our recent "Most Pathetic 360 Setup Contest."