I can certainly see how a vibrating collar, used purely to get attention (perhaps so you can then give a handsignal command) would give deaf dogs a far higher quality of life, as it would enable them to go off lead... I would imagine users would have to be very consistent in using it only to gain the dog's attention and not to interupt a behaviour (that could be a side effect, but would need to be used more often for positive attention to reduce the liklihood of it being associated with a negative reinforcement) - and always followed with a command so that the collar itself was not a command.....
In that sense it's no different to vibrating pads for fire alarms that are used for deaf people...
