Beta tester here. There's a built in ruler/selector for thickness. The temperature of the pan surface actually changes depending on the starting temperature of the salmon and given the conductivity of aluminium and the location of the embedded sensor, you do get a good approximation of the temperature at the interface not at the dial. The temperature actually drops immediately when you flip a piece of food or add something in, so the app can tell when you've done something. It's pretty neat!

It's true that if you start with a really dry/old salmon, this won't magically make it not dry.