They use a "near frictionless" rotor system which, to me, resembles a Rootes blower used for supercharging or other kinds of oil or pumping devices. Still, incremental refinement is often how the biggest advances occur (e..g TV, which did not contain a single new piece of technology, only a clever combination). It is basically using the same concept as an air conditioner or fridge, in that a compressed fluid with a very low boiling point is warmed, it boils, the pressure is used to drive the rotor and then it is sent back, cooler, to be warmed again. To me, if they can use this rotor, then a floating piston linear Stirling Engine could be used, but that is another issue.
The company talks of many uses but, for me, ignores the No1 use - automobile cooling systems. Use this device to scavenge the heat otherwise thrown away into the air by the engine radiator. Think of this in the context of a series hybrid, so that the engine will produce even more electricity as even more of the heat energy is being converted to electricity.
I hope they can miniaturise it for vehicle use. Cannot see why not, as it is basically an air-con unit tuned to be very efficient. Vehicle radiators operate at around 80-110degC (water is under pressure so it does not boil at that temp) so the temperature is within range. How about it, guys?