What about using loudspeaker paging and just having a speaker in the security office?
I was thinking over this and thought of 2 things
One was v2win's suggestion of paging (though I was thinking paging group of nominated handsets)
second option is if you have MiCC or some other sort of IVR, you could do a call flow that answers the call, then sends an email to nominated people/group then hangs up. Then they could use "Hotel/Motel Room Monitor Listen" FAC to listen in on the extension
