ice probe is using thermoelectric cooling. it uses a peltier element which when you run current, one side cools down, and the heat drawn from that heats up the other side. the cooling side is directly connected to a ceramic rod which is the side dipped in water, while the hot side is stacked against a heatsink, which had a fan to cool it. effectiveness also depends on your ambient temperature, on how you can cool down the heatsink (to allow more heat drawn from the other side to cool it down).