I think it is a good idea, my Dad died in exactly that way the only difference was it was the bathroom not the loo. He collapsed against the door and Mum could not get to him, the Dr's said that he was dead before he hit the floor, but Mum had to listen to the "rattle" of his last breaths from the other side of the door.
Even if this system was fitted he would not have survived, but Mum always say's she felt bad that his last breath was alone on a cold floor. The ambo's worked on him for 25 min's but they told me afterwards that he never had a chance and it was just what they have to do. They where very apologetic, but I was in the fire brigade at the time and I knew what was happening when they spoke to me.