Cool idea but I am not a fan of dogs wearing collars at home, especially if they are going to be alone or if there are multiple dogs.
Currently we use freezer flaps that hang from the top of the slider doorframe. This is in our sunroom and last night was the first night we had to close the door to the main house because of the cold. We would have closed the slider but it was full of dirt/sand. Anyway, it went down to the low 20's last night and the sunroom dropped to about 57. The room has heat but we decided not to turn it on because the dogs sleep in our room.
