Interesting but their explanation of how the widget works in wrong AFAIK. The widget is a small sphere with a small hole in it. It is put into the can presumably filled with something other than air (no oxygen wanted) but at atmospheric pressure. The can is then filled with carbonated stout and a couple of drops of liquid nitrogen are shot in and the can quickly sealed. It then goes into the pasteurization tunnel where it is heated briefly. This causes the nitrogen to turn to gas which, as it isn't very soluble in stout causes an appreciable rise in the pressure in the can. As the pressure in the can is higher than the pressure in the widget beer flows into the widget until the pressure is equalized. The can is cooled, shipped and winds up in your fridge. Even though cold, it is still at appreciable pressure both because of the nitrogen and the dissolved CO2 at equilibrium with the head space. When the seal is popped the pressure in the can drops suddenly to atmospheric but the pressure in the widget is still as high as it was before the can was opened. This causes the liquid and gas remaining in the widget to be expelled through the tiny hole which is oriented so that the widget spins resulting in a stream of liquid being fired through the beer causing the release of the classic tiny bubbles. That's the explanation I remember anyway.