Using regular thermometers, the temperature is only measured at the tip of the probe. This makes measuring the core temperature pretty complicated, as it requires you to hit the core of the meat precisely.
In fact, missing the core by just one centimetre can give a difference of up 10 degrees – the difference in cooking results from a Medium-rare to a Medium-done.
The CookPerfect monitors the temperature multiple places in the meat and then calculates the core temperature as well as the heat flow into the meat.