It's quite clear that dogs vocalize there feelings, even in reference to specific things, and that say yes/no to offers of things, and express their desires of (1) want or (2) want to avoid, quite clearly, and that vocalization alone is sufficient if one can't perceive the rest of their body language. While such a device would be superfluous for most people, it might help those who are in denial about dogs having feelings, to learn that they are mistaken, if they are subjected over a long period of time to the inescapable consistency between certain dog-produced sounds and the translation of them.