Yeah...I've seen something that would work...I'm trying to remember the company, though. Googling as we speak. Basically, the company just makes an IR remote-controlled power switch. All you would need to do would be to put it in-line on your main power switch. When you hit the button the remote, it closes the switch, and voila! you have power.
The only drawback and can find in this would be that you would have to use that as your main case power switch...unless you somehow made it possible to bypass it when you hit your case's main power switch...I see a schematic in the works!
I'll keep look for that company/product.
EDIT: OK! I know what would work...all you would need to do is rig an IR light switch that you can buy for your house. Not only does it allow on/off with an IR remote, but it also has a feature that allows you to push a button to turn it on/off. You would just wire that button directly to your computer's main power button.
That's my idea at least!