To make liquids flow more realistically, I propose:
-The creation of a new value called a liquid value.
-Every liquid pixel should be assigned a liquid value of 1
-A fixed number of (generally no more than 3, and depending on pressure) liquid pixels can clump together into a single pixel whose liquid value represents the total number of liquid pixels represented by the single pixel.
-These super pixels diffuse normally about the liquid (think soluble sponge).
-These 'super' pixels decay randomly into its constituent pixels only at the surface of the liquid. This decay rate is influenced by the pressure and viscosity. Higher pressure/viscosity=lower decay rate.
-Thus liquids can find their own level once they reach an equilibrium of clumping and decaying and thus can respond to pressure changes (e.g. a barometer)

*If it is too difficult to implement a new variable, the life value should serve just fine (except for lava, I know.)