IanBrown,
Yeah that is what I was thinking, but I wasnt sure if there were some specific sensors for my application. All the outdoor rated sensors Ive seen are square in shape and I wasnt sure how that would look on a round pole. I probably wouldnt even be doing this but we have a new puppy and, twice now, the gate has been left open and she went out on an adventure. We cant see this particular gate so it would be nice to know if it is open before she goes out. Thank you for the suggestions!