Hello,
Really depends on what OS your end users are working with on their computers. Windows 2003 Server, for example, has a shutdown command, that you can place a timer on and, work with. I don't think it has a place for a message, as interactive logins are not common on servers, unless you are running Terminal Services / Citrix. If you are running those applications, then you can message others using management tools contained within.
Looking at the problem from a network administration viewpoint, however, I do not like the idea of someone in another room just triggering a shutdown on me. I could be on a call supporting a customer, or I could be in a meeting and unable to save my data. Then again, you may have to decide to "amputate" that one user for the benifit of the greater good. If this becomes habit, you have other problems!
There is also a way to use the shutdown command across a network
shutdown /i
from a 2003 Server will give you a dialog box where you can add computers, give the users a warning of what you are up to. You would not be able to script this.
There is also
shutdown /r /m \\computername /t seconds /f {force shutdown, no warning}
If I were you, I would consider a remote control tool, such as VNC, that you can remotely trigger the service, and then login to the computer and see what the user is doing. Better manners suggest that you email or schedule the downtime, so that your users can plan for the event.
