Ethernet-attached extender for alarm sensors

With multiple network-connected buildings on the property it would be nice to monitor all with one alarm hub. An ethernet-attached (preferably) or wifi extender that communicate with the alarm-hub across the LAN would work where the distance is to far for a regular extender. As with everything Ethernet it should have PoE as an alternative power-source. An alternative solution may be to implement linked buildings using multiple networked alarm-hubs working together within the same site. This would also enable separate cellular backup-protection for secondary building(s).