Sounds like a job for a KVM switch...
Most laptops I've ever seen have VGA out.
Some monitors, I believe, have built-in TV tuners. Your mileage may vary.
Haven't been watching prices, but last I saw, a basic PCI TV tuner was about $30. No clue on the KVM; I tend to see them up at garage sales and ham fests for cheap.
"Users' expectations are higher than they used to be—if your interface isn't easy to use 'out of the box,' users will not think well of it...frustrated users can give up and switch to your competitor with just the click of a button. So the cost of building a mediocre interface is higher than it used to be, too." --Jenifer Tidwell, Designing Interfaces