We have several 46' Magicinfo-i machines in the often empty hallways of a public university, and somewhat fear theft.
We have something that does this.
Big Brother network monitoring software pings devices hooked up to the internet and sends an email if the pings fail. http://bb4.com/
I use it so that I know if the displays have locked up, been stolen, disconnected, or turned off. I have the email go to a gmail account, which forwards the mail as text messages to various cell phones.
One problem at this point is that the system seems to only ping at rather long intervals, say 20 minutes. Just started doing this, maybe we will figure out how to get a faster interval. Also, I think there is a free version of Big Brother out there.
Does anyone have anything better?