For many reasons I don't think a doggy door would be a good idea for me. Still I just saw a bit on a microchipped activated cat flap available in Europe and coming to the US. No doubt there will be versions for dogs soon. I think the fact that the dogs wont need an extra collar to activate a door is a great idea. It will keep other animals out and require no additional equipment for dogs that are microchipped, as they all should be.
Thanks for the information. I may get a door one day. As it is since the dogs exercise themselves outside, the main exercise I get is running up and down the stairs to let them in and out : )