I read about this a while ago, they have a layer of gas between the screen and digitizer and when the keyboard or any key is needed, it expands the gas at those areas and creates a bubble.
In order for it to really work well they digitizer will need to be plastic, plus they need to make sure there wont be any burn ins from repeated gas expansions.
I am really looking forward to this tech coming out, the big question is who will use it first, apple or motorola (using google bank account)
