InSite Relays are a feature that allows Site Manager to Site Manager communications through the Gate Manager server. This is to provide connectivity between devices that are not necessarily connected over the same network, such as that present for wireless and cellular connections.
One example of this would be for a SCADA connection. The SCADA server is connected to a Site Manager on a customer's corporate network, and a PLC is connected to another Site Manager located at a remote offsite location with 3G wireless access. With a Server Relay setup at the SCADA Site Manager, and a Device Relay set up at the PLC Site Manager, a connection can be established that allows the SCADA to poll the PLC at intervals.
Although limited to low-speed polling (on the order of 1 poll/sec), this allows a non-connected SCADA to access the data on Remote PLCs. This is without having to add any VPN or other firewall connectivity on either end - its already established through the Site Manager to Gate Manager connection.
For a typical tank farm application in this example, each tank would have a PLC or smart sensor coupled to a Site Manager with 3G wireless connectivity, and would periodically respond to data polling requests from a central SCADA server. This feature is in addition to the standard remote access and monitoring capabilities provided by the InSite system.