I use a TiPowerBook. I was pleasantly stunned awhile back when (by testing) I found that I could remotely start it up with an old iMac keyboard, the kind with a built in power button. Since I've just started using the computer as part of my home entertainment A/V hub (as I installed 100GB hard drive a year ago, it makes for a great video iPod!), so I can have the thing physically closed, but run it with this remote keyboard, including turning it on/off.
This seems like such a great feature that was abandoned. Why?
PowerBook G4's and I believe MacBook Pros still have this feature. Called closed lid operation, you have to have a USB keyboard, external video, and AC power hooked up. I did the same thing as you did with a 12" PB G4. I now use a MacBook Pro, but haven't tried it yet although I understand that it works too.
The on/off was a kludge that is not a part of the USB spec.