Automatic Chicken Door

I found this link for Chicory's post, thought I would put it here for future reference.
www.chickendoors.com

I got a similar model from England. Operates really well but doesn't always follow the hens' routine. Sometimes it would close when some were still outside and open before they were ready to leave the roost giving an opportunity for predators to enter. The manufacturer of this model has since added a delay timer, but I've never re-activated as not much point when I have 19 other doors to open and close.

Here's the link. They also have some other products that are useful.
http://www.chicken-house.co.uk/