NightFishNet
u/NightFishNet
What is your pfsense box plugged into on the WAN side? Since your WAN address is a private one, I'm guessing you have another router plugged into the WAN. If you have access to that, you could change the LAN subnet range on that to something else, and then use 192.168.2.0/24 on your pfsense LAN. If you do end up changing the LAN subnet on the upstream router, you can get pfsense to automatically grab a new IP by renewing the DHCP lease, or just reboot it if you're not sure how to do that :)
What is the motivation to use 192.168.2.0/24? Do you need to use that range or could you use something else?
As others have said wireless door sensor. It's not WiFi based so there would need to be some kind of base station or receiver somewhere nearby.
Also note that there is a magnetic reed switch on the circuit board which is probably a tamper switch. I'm guessing there is a magnet on the lid of the box so it knows when you open it. No clue whether the receiver is doing anything with that signal, but your landlord might know you've opened it in case that matters to you.
Edit: actually not sure about the tamper switch, another look seems like it may just allow the unit to be used standalone without an external sensor.