@M3 Convert Audi have developed a system for the 8Y whereby that the key knows whether it has physically moved or not. After a short time of no movement, the key (fob) becomes 'dead' and is not active to radio signals.
From what I take from this is that if you come home at 5pm, and by 5:15 the key is 'dead' and hasn't moved, if at 11pm someone tries to enhances the relay signal to the car it will not work unless the key have physically been moved within a certain period of time (not sure what the time is yet). So I think when the key is dead the car can only be opened by the fob itself if you move it/pick it up.