Good idea. Something like a magnetic switch hooked up to a zwave dry sensor. The wire can be run to the dry sensor thats in a shed or something somewhat out of the elements.

I just used this open/close magnetic sensor with a dry contact for my doorbell (pick up solinoid activation) and ran the wires to a closet on the opposite side of the wall.

Magnetic Switch https://www.amazon.com/dp/B0009SUF08/ref=cm_sw_r_cp_apa_6tNlAbQD00SSE

Aeotec by Aeon Labs ZW097 Dry Contact Sensor, Small, White https://www.amazon.com/dp/B0155HSUUY/ref=cm_sw_r_cp_apa_5xNlAbY3PARM7