The classic example of the equivalency principle is being inside an elevator where an acceleration is in indiscernible from a gravitational field. I'm thinking the elevator is a bad example though, and that the equivalence principle only holds for a single point in spacetime. If you have any distance to make a measurement, at the top and bottom of the elevator for example, you'll measure a gradient if you're in a gravitational field, but not if you're simply accelerating. Our current technology can measure a change in gravity with less than a centimeter of elevation change on the surface of the earth... a gradient that wouldn't exist if you were out at space and accelerating. Any thoughts, does this make sense?