For those of us who aren't technically inclined enough to assemble a custom rig, the Bothell, Wash.-based company GAEMS (Gaming and Entertainment Mobile Systems) has a more consumer-friendly solution. The G155 is a well-thought-out carrying case that fits the Xbox 360 (original and 360 S models), as well as the PlayStation 3 Slim.
The "case" is fitted with a 15-inch 720p LED-lit monitor, small integrated stereo speakers, and two 3.5mm headphone jacks, which should be good enough for the gamer on the road. While the unit doesn't provide power to your console of choice, it has sufficient storage space for the power adapters and cables you'll need.
We don't think the G155 is all that light at 8.6 pounds, minus the console, but GAEMS says it meets TSA requirements for carry-on luggage. It also costs nearly as much as your console at $299. It's available at Amazon.