The idea is it to have a remote controled item that can be placed on/instead of wires, which can toggle whether power does flow through the wire or not. It would allow a new type of mapping, where you would need to juggle your power for the station, by either powering every area, but having to micromanage every piece of equipment, to not totally drain the potential power, or have a centrally controled wirenet, where you can enable/disable areas. Maybe also do it with substation smess, where every department gets that charged, and then distributed into the APCs, which would allow to use the power from one department to boost another, to have the Star Trek feeling "Transfer life support to shields".
Another use would be as remote wirecutting/mending on doors. Currently, you can remotely pulse wires with signallers, but not cut the wire, which does limit your options a bit. It would also be nice as a mediator between two assembly items, a remote (de)activated mine would be possible that. Grenade with the ignition connected to the motion sensor with the relay, and you can remotely toggle it. Or if you have remote controled bombs, two people would need to authenticate it, EoC, which should get paroled, HoS says tracking+chem implant wouldn't cut it, they implant such a bomb into them, the code for the relay is only known to the Magistrate/Captain, or only accessable, if it has a fancy console to control, so they can authorise the "remote execution", and the HoS can activate it afterwards.
There also are two potential activation options, one beeing with the normal remote signaller frequency and code system, or a console similar to the central atmospherics computer, probably with diffrent levels of access/password protection. It could also get both systems, with a toggle on the relay itself.