Door/window sensors usually send a signal on state change from closed to open or the other way around. I think a leak sensor is more complicated because it nee

Door/window sensors usually send a signal on state change from closed to open or the other way around. I think a leak sensor is more complicated because it needs to detect a somewhat lowered resistance between the contacts, as opposed to the door sensors that will get a fully closed/opened reed switch on activation. Detecting lower resistance with some threshold in a battery powered device that needs to sleep most of the time is probably more complicated. I would guess waking up on a pin state change is built into most microcontrollers, while measuring resistance to make it wake up requires additional components?