Nose-phones. This might be more of a future sci-fi concept, unless some crazy folk are actually working on it.

You know how earphones/headphones can cancel out external noise while playing audio. What about "phones" that block external scents and odours and emits scents of their own that are isolated to the person wearing them? So not diffusers, scented candles or incense as everyone entering a room might smell but something far more personal.