well, it's quite a good idea, razor. by disallowing the system to shutdown by all but the administrator, one can have a monitoring program that sends out signals every particular interval to let the server know that system is still connected. when it misses an interval, an alarm can be issued which i guess can be sent via e-mail to administrator(s).
most motherboards now have hardware intrusion capabilities. meaning it can detect if the computer case is securely closed or opened. audible alarm will be issued should that event occur & the alarm feature is active. meaning that system must be switched on for that to happen.