it's how espresso steamers work too, raise it to near boiling point really quickly by using steam and the protein congeals around the bubbles.
Discussion
I like those machines. So sexy. So steampunk. I need one.
they aren't expensive. the pump that pushes the hot water through the coffee is more complicated. it's really easy to build one with an earlenmeyer, glass tube, stopper and a silicone hose. the vapor pressure of the steam does all the work