Please check PetFon and Whistle. As long as my siberian husky is no more than 1/4 to 1/2 mile away, Petfon works well. From my experience, in a thick PNW wood, its true life span is about 1/4 mile. In more open areas, it can reach 1/2 mile. The geo-fence alert was timely and I was able to keep...