A set of these devices could be mounted on gimbals and powered up and down and vectored to provide thrust in whatever direction and at whatever power levels was wanted. And since the EM Drive does not use any reaction mass, there is no exhaust and they can be mounted internally. With enough power, an EM Drive craft could even hover and move about noiselessly.
Eh... technically, there is reaction mass being ejected, it’s just that you don’t have to bring your reaction mass with you and it’s essentially endless. This is a pseudo-reactionless drive, really, and probably as close as we’re going to get until we figure out more physics.