How to transmit video card output wirelessly to a large screen TV?

How to transmit video card output wirelessly to a large screen TV?

I have a PC running Windows Vista (probably will upgrade to Windows 7 shortly) in one room of my home and a large screen HDTV in another. I can't run a line from the PC to the TV for various reasons and most of the time I'll continue to use the PC with its own monitor; but there are times I'd like to switch to the big screen (for gaming or occasionally for writing.)