This seems like a good use case for LoRa wireless modules, I haven't used them personally, but they claim a range of 10 miles without obstacles. Try searching f

This seems like a good use case for LoRa wireless modules, I haven't used them personally, but they claim a range of 10 miles without obstacles. Try searching for "LoRaWAN Door Bell" if you want off-the-shelf products, or otherwise for "Arduino + LoRa" if you want to DIY :-)