One of the central problems of cosmology is whether dark energy is a fixed cosmological constant or has a dynamical origin. The most straightforward way to test this is to precisely measure the equation of state. However, there are systematic limits to how well it can be measured. An alternative that allows precision measurement is the equivalence principle. In models of equivalence principle violation from dark energy, different measurements (i.e. the universality of free fall, variation of the fundamental constants and metric tests of gravity) are related. This talk presents general constraints for these models, and discusses how the present tight constraints could be naturally satisfied in scenarios with compact extra dimensions.