Hi Mister_Slowhand,
I’ve a similar configuration with StstemAlarm with arming function based on presence with device_tracker with smartphones in house, the alarm is armed at 23 in “home” mode (only perimetral door/windows sensors if device_tracker detect people in house), and the “away” mode is armed 5 minutes after any smartphone isn’t detected in home network (wifi and bt) and any movement are detected by human body sensor in house.
The problem is that device_tracker often is slow to detect when my wife enter in apartment.
So I need a solution to disarm system alarm manually.
Your solution with magnets is not secure, anyone can have a magnet to disarm system.
Initially I had thought to use a xiaomi smart switch hidden in a drawer of the cabinet of the entrance. but of course this system if discovered is usable by anyone … and I left it alone.
A solution could be to get it in your pocket and use like a remote controller… but I do not like it.
The Broadlink SC1 is only a switch like the Sonoff Basic.
At the moment the only practical and low cost solution seems to use a rfid RC522 reader and use the electronics of a xiaomi aqara door / windows sensor (which transmits via zigbee) or alternatively a Nodemcu flashed with Tasmota MQTT firmware (which transmits via wifi).
These components cost very little and are so small that they can be placed inside a box for electrical switches.
The problem is that I do not find any tutorial to build it with the xiaomi door / windows sensor … while for the Nodemcu there are many ideals on the net.
This solution seems more functional because I can use different badges, also programming different functions. For example, I could give one to the housekeeper, it could only work on Monday from 10 am to 2 pm, while my wife badge disarm always the alarm system.