I wonder if someone could make a system driven by vision recognition and other sensors that would open doors and let dogs and cats go out to the toilet on their own and then let them in again? These things driven on collars are a pain and the collars keep failing. So a vision system would be far far better in my view.
I wonder if anyone has already done it. There would also be a question of training. If a dog has normally been used to going to find a human and then having the human take the dog out, then the dog would have to be retrained to go to the door on its own. That might be very difficult to achieve unless the dog just picks it up accidentally. It might be difficult because your presence in the retraining process taking it to be near the door is just reinforcing the status quo - that you need to come with it. But if the dog were somehow to just go near to the door on its own and then see the door open magically then that could start the expectation / association process.
Much better than cat doors and dog doors. The door closing / opening engineering itself would be a nightmare unless done with very high quality mechanicals and electronic systems and the whole lot designed as a unit for this job.
Our two young tomcats love late evening, last-chance, dog-walk time. They go out when the dog goes out, and the cats run around crazily in the darkness, then coming back to the light where moths gather, jumping up and eating as many moths as they can. They look forward to the ritual. Then the dog comes upstairs to his dog bed in our bedroom. Buidheag sometimes needs to be evicted from the dog bed as the dog waits miserably. Humans are usually called in, with a pitiable look, to help here, but nowadays Buidheag has come to realise that she will inevitably get ordered out, so she tends to just give in when the dog looks at her, and just gets out. Then the kittens come racing up to the bedroom along with Caoimhe. Often there is an hour of crazy play racing around on top of and under the bed, and in and out of the bedroom door. Caoimhe meanwhile just stays cuddle up in my arm, as close as possible. When Somhairle decides it is time for sleep, Pangur Bàn is usually tormenting him for play still. Finally the tomcats curl up together, or sometimes all three oriantals in a heap. Sometimes, less often of late, Ciarán wants to go out to the toilet and is desperately waiting for Janet to get a move on and take him out. A high tech system would be very good at this time as he could go out as early as he likes, but only if retraining was successful.