I am looking for a relay or a switch that can disable access to a certain network segment remotely using a push button or interface of some sort. For example, there is a cat 5 communication line and a device somewhere along the line that acts as a relay. The intention of that relay is to physically break the connection. Does such a thing exist?
Home automation stuff, such as Insteon have relay that you can trigger remotely.
Break the connection to what, may one ask? If you just wanna disable Internet access to one PC, some smart/manage switches let you enable/disable individual ethernet ports, of course that won't stop any enterprising youngster to simply move his cable from one switch port to another.